Colloquium

In a closed many-body quantum system, the entanglement between individual degrees of freedom generally increases over time. This entanglement growth can be seen as a quantum analog of the second law of thermodynamics. On the other hand, probing the state of one of these degrees of freedom causes the wavefunction to collapse to a given outcome, thus disentangling it from the system. Thus, there is a competition between entanglement production due to internal dynamics and its reduction by measurement in monitored quantum systems, which leads to a phase transition in the thermodynamic limit, dubbed "The Measurement-induced Phase Transition." 

In this talk, I’ll begin by explaining how this transition can be interpreted as a classical percolation transition, which captures the universal behavior of the phase transition in certain limits. I'll then discuss our ongoing efforts to explore the nature of the transition beyond these limits, including small-system numerical studies, analyses using tree tensor networks, and large-scale numerical simulations with Clifford circuits.

Cooperation is vital for the survival of a swarm. No single bird is faster than a jet plane, and no single fish is faster than a speed boat — humans beat individual animals in air, land, and sea. But, when animals cooperate and swarm, they beat us since biblical times. The technological gap in engineering artificial swarms suggests a gap in our understanding of emergent behaviors in decentralized, distributed systems. Inspired by non-equilibrium statistical mechanics I will shed light on a hallmark of agile cooperation in nature — cooperative transport. Starting from the microscopic description of mechanically self-propelled particles, I will show that particles are expected to rotate by external forces. Coarse graining of the microscopic dynamics will lead to a set of equations of motion of Force Aligning Active Brownian Particles, which extends and generalizes existing models. Force-alignment is captured by a charge-like parameter with units of curvature that sets the tendency of the particle to align with or against an external force. Particles with a negative “active-charge” will turn in opposition and move against an external force or a repulsive potential. I will then argue that this minimal description can capture geotaxis — a widespread phenotype in individual insects that tend to climb uphill (i.e. move against the external force). I will then proceed to show how a swarm of Force Aligning Active Brownian Particles, spontaneously commence in the cooperative transport of a larger payload. Surprisingly, in both experiments in robotic swarms and numerical simulations, cooperative transport improves with increasing payload size. Using the effective equations of motion I will derive a non-linear dynamical system where cooperative transport is expected as a spontaneous symmetry breaking. I will present the resulting geometrical criterion for cooperative transport as the interplay of the payload’s geometrical curvature, and the “active- charge” of the self-propelled particles. Our findings offer new design rules for distributed robotic systems and shed light on cooperation in natural swarms.

We have entered a golden age in the study of astrophysical “transients” – short and often violent astronomical phenomena ranging from stellar explosions called “supernovae” to the powerful disruption of stars by black holes. The field of observational astrophysics, and specifically of transient science, is currently experiencing a “double revolution”: on the one hand, new cutting-edge telescopes are providing unprecedented copious and rich observations of transient phenomena; on the other hand, the developing field of data science is providing a plethora of new tools to analyze these observations. I will present two examples through which  we try to leverage the emerging opportunities for new discoveries and breakthroughs at this very critical moment in the history of the field. (1) Using innovative search algorithms, we try to mine decades of archival X-ray data in order to capture hidden signals originating from the very first moments of supernova explosions. These signals, which constitute a holy grail for astrophysicists, promise to reveal precious information about the stars ending their lives in spectacular explosions. (2) Using large amounts of new data from telescopes currently deployed in Space and on Earth, we seek to explore the links between supernova explosions and their environments, to get new insights into the unknown nature of exploding stars. 

Power grids are the backbone of modern society, yet they remain vulnerable to sudden surges in current – fault currents – that can damage equipment and trigger blackouts. Fault current limiters (FCLs) act as silent guardians, automatically mitigating these surges and safeguarding grid stability. This talk will delve into the world of FCLs, exploring the state-of-the-art in both resistive and inductive, superconducting and non-superconducting, FCL technologies.

The unique work being done at Bar-Ilan to push the boundaries of FCL performance will be described. We will discuss novel FCL designs, and the potential for these innovations to revolutionize power grid resilience.

Competition or cooperation between different electronic orders with similar energy scales often gives rise to new or unexpected behaviors. Detecting traces of such orders requires versatile probes, which can probe different aspects of the system, such as conductivity, superconductivity and magnetism. In my talk, I will describe a few systems where our local view uncovered surprising mesoscopic effects. I will focus on two polymorphs of a van-der Waals material, 4Hb-TaS2, in which we found a hidden magnetic phase, revealed by spontaneous vortices hosted by the superconductor, and 1T- TaS2, a switchable charge-density-wave system in which we found a surprising rearrangement of current flow. Overall, our results highlight the power of scanning SQUID microscopy in probing the properties of quantum materials and providing local insights into their behavior.

A bomb explodes when anything interacts with it: Can it be found without exploding it? Can we find that the bomb is not present in a particular place without any probe being there? Which tasks can be achieved without particles in the transmission channel: transmission of a classical message, teleportation of a quantum state, establishing a secret key? I will review the claims that these tasks can be done and will argue that only some of them are true. 

Friction is generally described by a single degree of freedom, a ‘friction coefficient’. We experimentally study the space-time dynamics of the onset of frictional motion when two contacting bodies start to slide. We first show that the transition from static to dynamic sliding is governed by rupture fronts (essentially earthquakes) that break the contacts along the interface separating the two bodies. Moreover, we show that the structure and dynamics of these ‘laboratory earthquakes’ is quantitatively described by singular solutions originally derived to describe the motion of rapid cracks under applied shear. We demonstrate that this framework essentially replaces the idea of a ‘friction coefficient’ as a description for the onset of frictional motion. Moreover, this framework quantitatively describes both ‘laboratory earthquake’ motion and arrest. The results establish a new (and fruitful) paradigm for describing friction and provide a fundamental understanding of how earthquakes develop, progress and eventually arrest.

The existence of dark matter has been well established with overwhelming evidence, but its particle identity remains unknown. Significant progress has been made in recent years in expanding the dark matter search to new uncharted territories. In this talk I will focus on the possibilities to probe dark matter terrestrially as well as indirectly, focusing, in part, on light and ultralight dark matter, which have been argued to be particularly motivated. I will briefly review the current status of the field and discuss new avenues in the search for dark matter.

Galileo Galilei is one of those larger-than-life heroes of our intellectual history. There aren’t many scientists, after all, whose lives and achievements inspired plays (such as Brecht’s Life of Galileo), scores of poems, or an opera (by Philip Glass). For Albert Einstein, Galileo was “the father of modern physics—indeed, of modern science altogether.”

I will trace Galileo’s fascinating life as I will examine his monumental achievements in astronomy, mechanics, and the development of the scientific method. I will also analyze his complex and tragic interaction with the Catholic Church, which had eventually led to Galileo being denounced a suspected heretic by the Inquisition.

I will emphasize Galileo’s relevance to a world in which anti-science attitudes have proliferated, and where there is a widening schism between the humanities and the sciences. Galileo’s life serves as a potent reminder of the importance of freedom of thought.

Renormalization group (RG) flows determine how the physics of a system depends on the length scale in which it is being probed. This is a fundamental concept in our understanding of any physical system. I will study how quantum chaos develops across different length scales in the Sachdev-Ye-Kitaev (SYK) model - a model of fermions with random couplings.  The model is special in that it is strongly coupled, chaotic and yet exactly solvable in certain limits.  The SYK model has gained significant interest in the past few years, both in the condensed matter community where it is proposed for modeling strange metal behavior and in high energy physics where it is proposed as a model for quantum gravity. I will explain how chaos develops across different length scales in the model. Time permitting, I will explain the relation of these results to black holes and quantum gravity.

The realization of a quantum computer represents a tremendous scientific and technological challenge due to the extreme fragility of quantum information. The physical support of information, namely the quantum bit or qubit, must at the same time be strongly coupled to other qubits by gates to compute information, and well decoupled from its environment to keep its quantum behavior.  

An interesting physical system for realizing such qubits are magnetic impurities in semiconductors, such as bismuth spins in silicon. Indeed, spins in semiconductors can reach extremely long coherence times - of the order of seconds. Yet it is extremely difficult to establish and control efficient gates between distant spins. Here we experimentally demonstrate a protocol where single spins can coherently transfer their quantum information to a superconducting device, which acts as a mediator or quantum bus. This superconducting device allows to connect distant spins on-demand without compromising their coherent behavior. 

References 

[1] M. Stern et al., Phys. Rev. Lett. 113, 123601 (2014). 

[2] T. Douce et al., Phys. Rev. A, 92, 052335 (2015). 

[3] A. Bienfait et al., Nature Nanotechnology, 282,1038 (2015). 

[4] T. Chang et al., Phys. Rev. Appl., 18, 064062 (2022). 

[5] T. Chang et al., Phys. Rev. Appl., 19, 024066 (2023). 

Photonic Time-Crystals (PTCs) are media whose electromagnetic properties are modulated periodically in time. When the modulation period is comparable to a single cycle of the wave propagating within them, and the modulation amplitude is at least 10-20% of the refractive index, the dispersion relation in PTCs exhibits momentum bands separated by significant momentum gaps. The momentum gaps are especially interesting – as they give rise to exponential amplification (and de-amplification) of the waves associated with those gaps, extracting energy from the modulation (or giving away energy to it).  This talk will review the basic concepts of PTCs and will focus on light-matter interactions, especially on light emission in PTCs. The last part of the talk will describe recent experimental progress on observing time-refraction within a single optical cycle, and on nonlinear phenomena in these time-varying media.

What is the force needed to crush a soda can? Surprisingly, there is no straightforward answer. From everyday items like soda cans to critical applications in aerospace engineering, accurately estimating the buckling loads for shell structures is crucial. However, these systems are extremely defect-dependent, and classical linear analysis frequently overestimates the buckling loads of cylindrical shells, leading to catastrophic failures. To address this challenge, we have developed a fully nonlinear framework inspired by research in turbulent flows. We tested this by smashing hundreds of commercial soda cans, such as Coke and Beer, and capturing the stability of shells through lateral probing to measure their stability landscape. Our results introduce a practical, fully nonlinear paradigm for understanding the fundamental processes that lead to catastrophic failure in shells.

After a brief period of free and fair---if imperfect---elections in Russia in the 1990s, the 2000s saw a resurgence of Soviet-bloc practices in which the desired result is attained through purely administrative means up to and including direct falsifications. I will show how to reveal and quantify these falsifications by applying simple statistical tools to fine-grained election data. I will also present a couple of examples from other post-Soviet countries.

NOTE: The views and opinions expressed in this talk are those of the speaker and do not necessarily reflect the official policy or position of the university.

Despite the huge success of the Standard Model of particle physics, it is not a complete description of Nature. It cannot account for several experimental results and observations and there are strong theoretical arguments that call for new physics. In this talk, we will discuss novel methods to hunt for new physics beyond the standard model at different energy and length scales, from atomic physics to future colliders.

Recent observational successes are providing a new impetus to the study of binaries containing stellar-mass black holes.  I will start with a very brief review of the current understanding of massive binary evolution leading to the formation of black-hole binaries.  I will then focus on a few of the outstanding issues in interpreting both X-ray and gravitational-wave observations and propose pathways for improving our understanding of some challenging aspects of binary evolution.

Active systems are driven out of equilibrium by consuming energy and dissipating it into the environment. This endows them with anomalous mechanical properties, very different from equilibrium systems, that lead to rich physics when they interact with boundaries, bodies (inclusion), or disordered potentials. While on the one hand, active systems can propel, and rotate bodies placed in them, the bodies also have a non-trivial influence on active fluids. This is best exemplified by the propensity of bulk and boundary disorder to destroy phases in active matter, showing active systems to be much more sensitive to their surroundings than equilibrium ones. The colloquium aims at providing a unifying perspective on the rich interplay between active systems and their environments using the simplest class of active systems.

Tidal Disruption Events (TDEs) are cosmic occurrences where a star is torn apart by the immense gravitational forces of a supermassive black hole. This field is one of the key focus of contemporary astrophysical time-domain research, which offers critical insights into the nature of black holes, the dynamics of stellar destruction, and accretion physics. In my talk I will review our current understating of TDEs, and will address some challenges and pressing questions in the field. I will present new recent discoveries such as the (highly debated) association of neutrinos with TDEs, and my own discovery of delayed radio flares. The latter phenomenon shows that radio emission from TDEs can turn on sometimes months, and even years after stellar disruption. While we identified some possible explanations, the nature of these flares still remains mostly unknown. I will conclude by discussing future avenues in TDE research.

Ecosystems are arguably the most complex but least understood level of biological organization. Microbial communities, composed of numerous interacting species, are of particular importance as they play key roles in numerous application areas, including biotechnology, agriculture, and medicine. In this talk, I will discuss our efforts toward developing a predictive understanding of the structure and function of microbial communities. We found that a pairwise approximation of interspecific interactions is sufficient for predicting community structure in laboratory microbial communities. Furthermore, using high-throughput microfluidics, we show that interactions typically change qualitatively across environments, but can be predicted based on the growth abilities of individual species. These findings provide the first step toward “synthetic ecology”—the rational design and management of microbial communities.

The task of understanding the dynamics of the immune system has been gaining increasing importance, as a consequence of progress in immunotherapy applied to cancer and due to the importance of vaccines, as with the COVID-19 pandemic. This talk will survey examples which show physics can help address some of the important conceptual and also practical issues that arise in this research area. Specific issues to be discussed includes the detection of neoantigens (immune-activating enzymes on the outside of a cancer cell) as a way to target tumor cells, the spatiotemporal dynamics of immune cell infiltration into tumors, the ecology of the immune microenvironment and the role of evasion by both cancer cells and evolving viruses.

The geomagnetic field, one of the most enigmatic phenomena in Earth Sciences, is constantly changing. Our knowledge about it in periods prior to instrumental recording is based on geological and archaeological materials, the latter provide the highest resolution for the last 10,000 years. In this talk we will demonstrate how archaeology helps to better understand the geomagnetic field, including the discovery of the “Levantine Iron Age geomagnetic Anomaly” (LIAA), and how in turn our information on regional changes in the field helps to develop an efficient dating tool for archaeology.

A theoretical framework for the percolation of interdependent networks will be presented. In interdependent networks, such as infrastructures, when nodes in one network fail, they cause dependent nodes in other networks to also fail. This may happen recursively and can lead to a cascade of failures and to a sudden fragmentation of the system. This is in contrast to a single network where the percolation transition due to failures is continuous.  I will present analytical solutions based on percolation theory, for the functional network and cascading failures, for a network of n interdependent networks. Our analytical results show that the percolation theory of a single network studied for over 80 years is just a limited case, n=1, of the general and a significantly richer case of n>1. I will also show that interdependent networks embedded in space are significantly more vulnerable and have significantly richer behavior compared to non-embedded networks. In particular, it will be shown that localized attacks of zero fraction but above a microscopic critical size lead to cascading failures that dynamically propagate like nucleation and yield an abrupt phase transition.  I will finally show that the abstract interdependent percolation theory and its novel behavior in networks of networks can be realized and proven in controlled experiments performed by Aviad Frydman on real physical systems.  I will present recent experiments that support the interdependent network theory in measurements of interdependent superconducting networks where a novel abrupt transition is observed due to microscopic interactions between the macroscopic systems although each isolated system shows a continuous transition.

References
S. Buldyrev, G. Paul, H.E. Stanley, S. Havlin, Nature, 464, 08932 (2010)
J. Gao, S. Buldyrev, H. E. Stanley, S. Havlin, Nature Physics, 8, 40 (2012)
A. Bashan et al, Nature Physics, 9, 667 (2013)
A Majdandzic et al, Nature Physics 10 (1), 34 (2014); Nature Comm. 7, 10850 (2016)
M. Danziger et al, Nature Physics  15(2), 178 (2019)
B. Gross et al, PRL  129, 268301 (2022)
I. Bonamassa, B. Gross, A  Frydman et al, Interdependent superconducting networks, Nature Physics (May 1, 2023)

Can Physics assist with key challenges in Neuroscience and Artificial Intelligence? Are current theoretical techniques of statistical mechanics capable of dealing with brain dynamics? Let us swim against the stream when scientific evidence tells you something is wrong.

Century-old assumptions regarding neurons and brain learning are disproved. According to the long-lasting computational scheme, each neuron sums the incoming electrical signals through its dendrites and when the membrane potential reaches a certain threshold the neuron typically generates a spike. We present several types of experiments, indicating that each stochastic neuron functions as a collection of independent threshold units, where the neuron is anisotropically activated. In addition, experimental and theoretical results reveal a new underlying non-local mechanism for the fast brain learning process, dendritic learning, as opposed to learning which is based solely on slow synaptic plasticity, where just one single neuron can realize deep learning algorithms. Though the brain is a very slow machine, its capabilities exceed typical state-of-the-art ultrafast artificial intelligence algorithms; hence, a revolution in deep learning must emerge.  

Laser Plasma Accelerators (LPA) rely on our ability to control finely the electrons motion with intense laser pulses. Such manipulation allows to produce giant electric fields with values in the TV/m exceeding by more than 3 orders of magnitude those used in current accelerator technology. Controlling the collective electrons motion permit to shape the longitudinal and radial components of these fields that can be optimized for delivering high quality electrons beam or energetic photons.

To illustrate the beauty of laser plasma accelerators I will explain the fundamental concepts we recently discovered, with also some recent results from the Weizmann Institute of Science, and I’ll show the maturity of our approach in delivering particle and radiation beams for societal applications including for radiotherapy with the ebeam4therapy EIC project.

The launch of ChatGPT has been a remarkable milestone in the development of artificial intelligence (AI) and has captured widespread attention. However, current computing hardware presents limitations for AI development, particularly for edge computing. Neuromorphic computing systems, utilizing in-memory analogue computation, are a promising solution that is attracting significant interest. Among them, a spintronic realization based on a magnetic tunnel junction (MTJ) crossbar is gaining momentum. Unfortunately, the current MTJs are constrained to only two resistance states, posing significant limitations. In this talk, I will present our research efforts towards developing a new type of MTJ that supports multiple resistance states, facilitating the realization of a significantly more efficient spintronic crossbar to be used in future AI applications.

The Poisson-Boltzmann theory stems from the pioneering works of Debye and Onsager and is considered even today as the benchmark of ionic solutions and electrified interfaces. It has been instrumental during the last century in predicting charge distributions and interactions between charged surfaces, membranes, electrodes, macromolecules, and colloids. The electrostatic model of charged fluids, on which the Poisson-Boltzmann description rests and its statistical mechanical consequences have been scrutinized in great detail. Much less, however, is understood about its probable shortcomings when dealing with various aspects of real physical, chemical, and biological systems. After reviewing the Poisson-Boltzmann theory, I will discuss several extensions and modifications to the seminal works of Debye and Onsager as applied to ions and macromolecules in confined geometries. These novel ideas include the effect of dipolar solvent molecules, finite size of ions, ionic specificity, surface tension, and conductivity of concentrated ionic solutions.

Despite hundreds of searches for physics beyond the standard model (BSM), and hundreds of person years invested, no confirmed deviation from the standard model (SM) has been observed. Yet, the LHC data is far from being fully explored and BSM physics could be easily hidden in the already collected data. This calls for the development of new search approaches and methods. The Data Directed Paradigm (DDP) presented in this talk is one possible approach. While the DDP can be implemented exploiting different properties of the SM, here we discuss its implementation for symmetries of the SM. Its performance is demonstrated relative to traditional searches for lepton flavor violation and lepton non universality. 

In recent years many candidate setups have been proposed to support exotic quasi-particles, such as Majorana fermions (MFs), which may be relevant for quantum computing, but whether these particles have been observed experimentally is currently a topic of a vivid debate. Entropy measurements can unambiguously separate these quasi-particles from other, simpler excitations. The entropy of a MFs is, for example, log2/2 (in units of the Boltzman constant), a fractional value that cannot be attributed to a localized excitation. However, standard entropy measurements applicable to bulk systems cannot be utilized in measuring the additional entropy of a mesoscopic device, which may be due to less than a single electron in the device. In this talk I will describe recent theoretical and experimental progress in performing such measurements, either using thermopower and/or using the Maxwell relations [1,2]. Particular examples will be single and double quantum dots in the Coulomb blockade regime. Lastly I will show how the formalism has been generalized to deduce the entropy from conductance measurements, and, applying it to a setup where two and three-channel Kondo physics have been observed, yields the fractional entropy of a single MF and a single Fibonacci anyon [3].  Lastly I will discuss the backaction of the measurement and discuss the possibility of measuring entanglement entropy [4].

[1]    Direct entropy measurement in a mesoscopic quantum system, N. Hartman, et al.,  Nature Physics 14, 1083 (2018).
[2]    How to measure the entropy of a mesoscopic system via thermoelectric transport, Y. Kleeorin et al., Nature Comm. 10 , 5801 (2019)
[3]    Fractional Entropy of Multichannel Kondo Systems from Conductance-Charge Relations, C. Han et al., Phys. Rev. Lett. 128, 146803 (2022).
[4]    Realistic protocol to measure entanglement at finite temperatures, C. Han, Y. Meir and E. Sela, Phys. Rev. Lett., 130, 136201 (2023).

Fluctuations of parameters that are ubiquitous in any real medium have pronounced, sometimes determining effect on the transport of wave radiation and quantum particles. Commonly encountered in nature is the diffusive regime, which has been extensively investigated for a long time, and nowadays is deemed to be well understood. Theoretically, it is usually studied in the framework of diffusion equations, which have proven to be quite efficient in explaining a wide variety of phenomena and experimental results in optics, acoustics, solid state physics, astronomy, biology, financial mathematics, etc. However, the issue with those equations is that they typically deal with ensemble-averaged quantities, which often have a little to do with the observations at a single random realization. Recently, it was discovered that, contrary to the common longstanding belief, the intensity of radiation propagating in a diffusive medium is not always homogeneously distributed. Under certain conditions, it is significantly structured: localized in the transverse direction in relatively narrow separated transmission channels, which are stretched along the sample and transmit the energy almost without leakage. The transmission coefficients and the incident and outgoing waveforms of these channels are given by the singular value decomposition of the transmission matrix, which connects the normal modes at the input to those at the output of a random sample. The unique physical properties of transmission channels open up new avenues for controlling the energy transmission and distribution inside a random medium, and for using it as a useful optical element. In my talk, a brief history and the current state of art in studying of the wave transport in diffusive media will be presented.

Trapped-ions are one of the leading platforms for quantum computing technology with errors in the 10^-6-10-³ level . In this colloquium Ill review basic methods and the status of trapped-ion quantum computing: different quantum gate schemes,  ion-trap fabrication and scale-up strategies. Ill also present recent results from our lab in which many-body coherent-control techniques are used to execute multi-qubit, robust gates.

A thin sheet that has been crumpled many times exhibits many of the hallmark behaviors of driven and nonequilibrium disordered systems: intermittent global responses, emission of correlated crackling noise, slow relaxations and aging, and a range of mechanical memory effects. Here, through experiments in thin crumpled sheets and simulations of a minimal mechanical model, we reveal a microscopic, real-space, structural mechanism underlying and linking these behaviors.

Using experiments that combine global mechanical measurements, local probing, acoustic measurements, and 3D imaging of crumpled sheets, we build a mesoscopic description of their mechanics. The global measurements reveal a range of memory effects, including hysteresis, memory of largest strain, and return point memory, as well as clear signatures of underlying intermittent dynamics. Intermittent dynamics are also observed during slow, logarithmic aging of crumpled sheets under load. In this case, however, the intermittent events are grouped into highly correlated, scale-free avalanches. The complimentary local measurements reveal that intermittency, memory, and aging behaviors emerge from the collective dynamics of mesoscopic, bistable elements within the sheet: localized geometric instabilities that act as coupled, hysteretic, two-state degrees of freedom.

Based on this picture, we develop a numerical model of a disordered network of bistable elastic elements that corroborates all our findings: hysteresis, intermittencies, memory formation, return point memory, slow relaxations, aging, and avalanches. The model highlights the role of interactions and frustration between instabilities in driving these behaviors. The emerging picture is of a disordered system with a complex energy landscape, reminiscent of a mechanical spin-glass, that self-organizes to a state which lies on the verge of instability.

References:

Shohat, D., Hexner, D. & Lahini, Y. Memory from coupled instabilities in unfolded crumpled sheets. Proc National Acad Sci 119, e2200028119 (2022).

Shohat, D. & Lahini, Y. Dissipation Indicates Memory Formation in Driven Disordered Systems. Phys Rev Lett 130, 048202 (2023).

Lahini, Y., Rubinstein, S. & Amir, A. Crackling noise during slow relaxations in crumpled sheets (in review)

Shohat. D., Friedman, Y. & Lahini, Y. Aging on the edge of stability in disordered mechanical systems (in review)

The re-invigorated field of electron hydrodynamics in quantum matter has recently garnered considerable scientific interest, both due to its technological promise of designing near dissipation-less nanoelectronics, as well as its fundamental importance as an experimental probe of strong electron-electron interactions. Investigating the capacity to which observations of electron hydrodynamic flows can inform the nature of electron-electron interactions is particularly important and timely with the advent of spatially-resolved transport measurements which, having demonstrated the hallmark spatial signature of electron hydrodynamic channel flow, must now turn their attention to studying more spatially-complex geometries, enabling the observation of intricate fluid phenomena such as vortices. Recently we have explored the effects of crystal symmetry on electron fluid behaviors starting from the most general viscosity tensors in two and three dimensions, constrained only by crystal symmetry and thermodynamics. In our work we demonstrate the anomalous landscape for electron hydrodynamics in systems beyond graphene, highlighting that previously-thought exotic fluid phenomena can exist in both two-dimensional and anisotropic three-dimensional materials with or without breaking time-reversal symmetry. In this context, the first part of my talk will discuss our recent predictions of hydrodynamics beyond graphene, especially the role of phonons in hydrodynamics in Weyl semimetals. We identify phonon-mediated electron-electron interactions, computed with techniques developed in the group that I will discuss in this talk, as critical in a microscopic understanding of hydrodynamics. The second part of my talk will introduce a new theoretical and computational transport framework from our group, the SpaRTaNS (Spatially Resolved Transport of Nonequilibrium Species) framework. I will discuss applications of this method in nonequilibrium electron and phonon transport in quantum matter. Time permitting, building on our recent work in magnetic Weyl semimetals, I will discuss possible approaches to understand and realize axion physics in condensed-matter systems.

References and links:

SpaRTaNS: Link to Github https://narang-lab.github.io/spartans/

1. Varnavides, G., Jermyn, A. S., Anikeeva, P., Felser, C. & Narang, P. Electron hydrodynamics in anisotropic materials. Nat. Commun. 11, 1–6 (2020).

2. Vool, U. et al. Imaging phonon-mediated hydrodynamic flow in WTe₂. Nat. Phys. 17, 1216–1220 (2021).

3. Varnavides, G., Jermyn, A. S., Anikeeva, P. & Narang, P. Probing carrier interactions using electron hydrodynamics. arXiv [cond-mat.mtrl-sci] (2022).

4. Varnavides, G., Wang, Y., Moll, P. J. W., Anikeeva, P. & Narang, P. Finite-size effects of electron transport in PdCoO₂. Phys. Rev. Mater. (2021) doi:10.1103/physrevmaterials.6.045002.

5. Wang, Y. & Narang, P. Anisotropic scattering in the goniopolar metal NaSn2As2. Phys. Rev. B Condens. Matter 102, (2020).

6. Osterhoudt, G. B. et al. Evidence for Dominant Phonon-Electron Scattering in Weyl Semimetal WP2. Physical Review X vol. 11 Preprint at https://doi.org/10.1103/physrevx.11.011017 (2021).

7. Coulter, J. et al. Uncovering electron-phonon scattering and phonon dynamics in type-I Weyl semimetals. Phys. Rev. B Condens. Matter 100, 220301 (2019).

8. Garcia, C. A. C., Nenno, D. M., Varnavides, G. & Narang, P. Anisotropic phonon-mediated electronic transport in chiral Weyl semimetals. Phys. Rev. Materials 5, L091202 (2021).

9. van Delft, M. R. et al. Sondheimer oscillations as a probe of non-ohmic flow in WP2 crystals. Nat. Commun. 12, 4799 (2021).

10. Coulter, J., Sundararaman, R. & Narang, P. Microscopic origins of hydrodynamic transport in the type-II Weyl semimetal WP2. Phys. Rev. B Condens. Matter 98, (2018).

11. Varnavides, G., Jermyn, A. S., Anikeeva, P. & Narang, P. Nonequilibrium phonon transport across nanoscale interfaces. Phys. Rev. B Condens. Matter 100, 115402 (2019).

12. Zhao, B., Guo, C., Garcia, C. A. C., Narang, P. & Fan, S. Axion-Field-Enabled Nonreciprocal Thermal Radiation in Weyl Semimetals. Nano Lett. 20, 1923–1927 (2020).

13. Nenno, D. M., Garcia, C. A. C., Gooth, J., Felser, C. & Narang, P. Axion physics in condensed-matter systems. Nature Reviews Physics 2, 682–696 (2020).

14. Mu, Q.-G. et al. Suppression of axionic charge density wave and onset of superconductivity in the chiral Weyl semimetal Ta2Se8I. Phys. Rev. Mater. 5, (2021).

Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are relatively young, isolated neutron stars, that are thought to have super-strong ($10^{14} – 10^{15}$ G) dipole magnetic fields and even larger internal toroidal magnetic fields.  Thus, they were given the name Magnetars.  I will examine if this is a fact or possible fiction.  I will present an alternative picture and I will discuss what it will take to decide between the two pictures.

References:

https://ui.adsabs.harvard.edu/#abs/2013ApJ...764...49T/abstract
https://ui.adsabs.harvard.edu/#abs/2014A%26A...562A..62K/abstract

Spontaneous parametric down-conversion is the workhorse of quantum optics. It is used to generate entangled photon pairs and heralded single photons. When strongly pumped, spontaneous parametric down-conversion generates so many photon pairs that they overlap and form radiation with almost laser brightness. Nevertheless, this radiation manifests nonclassical effects: quadrature squeezing, photon-number correlations, and macroscopic entanglement. It has no coherent component and can be considered as amplified vacuum noise; it is therefore often called bright squeezed vacuum. In addition, strong photon-number fluctuations of bright squeezed vacuum make it extremely efficient for pumping multiphoton effects.

In my talk I will describe the quantum features of bright squeezed vacuum, and our recent experiments where we use it to pump multiphoton effects: optical harmonic generation and multiphoton photoelectron emission from nanotips. Further, I will speak about nonlinear interferometry, where two sources of parametric down-conversion are placed one after another to measure phase disturbances or absorption in between. Finally, I will show how a strongly pumped parametric amplifier can be used for the tomography of a quantum state, with immunity to loss and imperfect photodetection.

For thousands of years, the Mediterranean Sea connected the people that lived along its shores – ancient coastal cities, ports and anchorages, shipwrecks and their cargoes, are all material evidence of human activity. The archaeological remains discovered on the seabed are cultural assets denoting the relationships that existed between man and the sea, and are an important pillar in the study of the history and archeology of the Mediterranean basin. A sunken ship represents a moment frozen in time, and underwater archaeology can offer a unique opportunity to explore and study this ‘time capsule’. The study of a shipwreck site can contribute new and valuable information on various aspects of seafaring, and enrich our understanding of the past. An overview of underwater excavations of ancient shipwrecks in Israel will be presented, followed by three case studies: the Ma‘agan Mikhael II replica ship; the holding power of Bronze Age stone weight anchors; and the 19th century Akko 1 shipwreck.

I will describe the results of a series of works in which we have found systems for which Spontaneous Symmetry Breaking(SSB) persists to very high temperatures. 
The systems involve Conformal Field Theories of scalars in fractional dimensions 3<d<4-\epsilon and for Gauge Theories in d=4.
The systems are studied in the limit of various large numbers of species. In the process we have found non supersymmetric
conformal manifolds as well as cases of non supersymmetric effective potentials with flat directions. The SSB results in the formation of a dilaton. We also discuss  some phase diagrams in the presence of relevant and marginally relevant operators made out of scalar fields in d=4.

Statistical physics successfully accounts for phenomena involving a large number of components using a probabilistic approach with predictions for collective properties of the system. While biological cells contain a very large number of interacting components, (proteins, RNA molecules, metabolites, etc.), the cellular network is understood as a particular, highly specific, choice of interactions shaped by evolution, and therefore difficultly amenable to a statistical physics description. Here we show that when a cell encounters an acute but non-lethal stress, its perturbed state can be modelled as random network dynamics. Strong perturbations may therefore reveal the dynamics of the underlying network that are amenable to a statistical physics description. We show that our experimental measurements of the recovery dynamics of bacteria from a strong perturbation can be described in the framework of physical aging in disordered systems (Kaplan Y. et al, Nature 2021). Further experiments on gene expression confirm predictions of the model. The predictive description of cells under and after strong perturbations should lead to new ways to fight bacterial infections, as well as the relapse of cancer after treatment.

A ubiquitous property of ultracold gases is the tunability of two-body interactions. When these interactions are resonantly enhanced, the quantum mechanical scattering problem supports weakly bound three-body states with universal properties. The latter means independence of details of the short-range interaction potentials and a discrete scaling invariance. Various aspects of this universality have been successfully demonstrated theoretically and experimentally in several atomic species in a recent decade. Lithium, however, remains a notable exception stubbornly refusing to concur with the emergent framework. In this talk I shall overview the subject and describe an increasingly involved theory-experiment collaborative effort to reveal the physics responsible for this puzzling behavior. 

Human-associated and environmental microbial communities play important roles in their ecosystems. These communities consist of trillions of micro-organisms of typically hundreds of different taxa, which interact with each other and with their environment, represented as tangled ecological networks. Understanding these networks is key to understanding their dynamics and developing control strategies. However, reliable reconstruction of such large networks is a very challenging task, especially where the available data is limited. In my talk, I will review recent studies where we developed and applied a top-down approach to studying microbial networks, such as the `universality’ of their dynamics [1], their `effective connectivity' and its relation to May's stability criterion [2], detection of keystones [3], and if time permits, I will briefly present new results on the analysis of single-time-point microbial samples.

1) Universality of human microbial dynamics, Bashan A. et al, Nature (2016).
2) Complexity–stability trade-off in empirical microbial ecosystems, Yonatan Y. et al, Nature Ecology & Evolution (2022).

3) Top-down identification of keystone species in the microbiome, Amit G. and Bashan A., bioRxiv

Novel phases of matter can emerge when electrons are confined to two-dimensions, and have a significantly reduced kinetic energy relative to their interaction energy. The remarkable discovery of numerous interacting phases of matter, including superconductivity, in highly tunable devices made out of graphene and other semiconducting materials in recent years are challenging many of our established theoretical paradigms. I will begin by highlighting the conceptual difficulties with describing superconductivity in the limit where the electronic kinetic energy is quenched, where the standard theory due to Bardeen-Cooper-Schrieffer no longer applies. I will address the “universal” ingredients that set the superconducting transition temperature, in this non-perturbative limit. I will also revisit an old experimental puzzle in condensed matter physics, namely how a metal--an electrical conductor--transitions continuously into an electrical insulator with increasing strength of electronic interactions, inspired by experiments at Cornell.

Dark matter is one of the biggest mysteries of modern day physics, yet its identity remains unknown. In this talk, I will focus on light dark matter. From the theory side, I will discuss new theoretical developments that suggest light dark matter. From the experimental side, I will present new proposals for the direct detection of light dark matter which hold much promise. These include the use of superconducting nanowires, two-dimensional targets such as graphene, and heavy fermion materials. Considering dark matter interactions with these targets, I will demonstrate the potential of the light dark matter direct detection program in upcoming years.

The photonic effort is one of the leading candidates for universal quantum computing. In particular, it is the only technology that has been originally designed to reach the massive scaling required for fault-tolerant universal quantum computation (> million physical qubits). In my talk I will describe the photonic approach, which combines topological error correction and measurement-based quantum computation. I will then describe how cavity-QED with single atoms can drastically simplify this effort, solve its main bottleneck, and improve its scaling to even larger numbers of physical qubits.

References
1) Fusion-based quantum computation: arXiv:2101.09310 [quant-ph]
2) Photon-Atom Qubit SWAP gate: Nature Physics 14 996 (2018)

Living cells with identical genome exhibit variability in their physical and functional properties. This variability is generated by cell proliferation (i.e. cells become different from each other over time as they grow and produce offspring), which suggests that properties are unreliably inherited between consecutive generations. But what is the extent of unreliability of inheritance? Do cellular properties exhibit Markovian dynamics, or do they have long-term memory? Obtaining quantitative answers to these questions will enable us to uncover the sources that contribute to generating variability among genetically identical cells. It will also allow us to develop accurate description of how the properties of cells will change over time. In this talk I will present our study in which, we measure the inheritance dynamics in bacteria, and reveal how it contributes to regulating various cellular properties (size, growth rate, etc.) in future generations. This is achieved using a new novel microfluidic device that enables us to track how sister cells become different from each other over time. Our measurements provide the inheritance dynamics of different cellular properties, and the ‘inertia’ of cells to maintain these properties along time, i.e. cellular memory. We find that certain cellular properties exhibit long memory that extends up to ∼10 generations.

Gravitational lensing (GL) has played various key roles in physics and astronomy, from the first proof for general relativity, to highlighting the need for a dark matter component. GL is currently used for a range of science from mapping the invisible dark matter to detecting exo-solar planets. In this talk I will review recent advancements in GL-related science. Among these, are the lensing of distant stars, supernovae, gamma-ray bursts, fast radio bursts, and gravitational waves. I will highlight key results mainly with respect to insights on dark matter and on the first galaxies in the universe, as well as our contribution to these fields and the relation to the recently launched James Webb Space Telescope.

Much interest is attracted nowadays towards quantum computers. Both academy and industry wish to develop the right hardware and software which could benefit the most from the principles of quantum mechanics. However, many questions are still open, namely, why is it that only special problems have, at the moment, efficient quantum algorithms to solve them? Why is the advantage that quantum algorithms provide, compared to classical ones, vary so much from problem to problem? What are the most fundamental ingredients that make a quantum algorithm successful and what is the optimal balance between them? How can we systematically devise new quantum algorithms?

These are hard problems, which I cannot fully solve at the moment, but 1) I think that they are interesting and important. 2) I feel that we should discuss them more often these days. 3) I would like to present in my talk some suitable background and then our first attempts at solving them.

After a general overview I will present some unique quantum features underlying quantum algorithms, e.g. quantum nonlocality [1,2], uncertainty and non-commutativity [3], quantum discord [4], and mostly, irrealism [5]. I will then address our more recent approach which attempts to analyze quantum algorithms as communications channels via the mutual information between the output of the computer and the parameter it wished to find or estimate.

[1] Carmi A., Cohen E.,"Relativistic independence bounds nonlocality", Sci. Adv. 5, eaav8370 (2019).
[2] Cohen E., Carmi A., "In praise of quantum uncertainty", Entropy 22, 302 (2020).
[3] Carmi A., Herasymenko Y., Cohen E., Snizhko K., "Bounds on nonlocal correlations in the presence of signaling and their application to topological zero modes", New J. Phys. 21, 073032 (2019).
[4] Peled B.Y., Te'eni A., Carmi A., Cohen E., "Correlation Minor Norm as a Detector and Quantifier of Entanglement", Sci. Rep. 11, 2849 (2021).
[5] Paiva I. L., Dieguez P. R., Angelo R. M., Cohen E., "Coherence and realism in the Aharonov-Bohm effect", under review in Phys. Rev. A, arXiv:2209.00480.

There are various approaches to gain insights at the macromolecular level from fluorescence-based assays, some of which depend on the structure of the fluorophores and photophysical effects they exhibit stemming from their structure. The effect of excited-state cis-trans isomerization occurring in fluorophores that act as molecular rotors in excited-state can be used if the de-excitation of one isomer exhibits high fluorescence quantum yield while the other exhibits a lower fluorescence quantum yield. In photoisomerization-related fluorescence enhancement, or PIFE, the potential steric obstruction of isomerization and its effect on fluorescence is used for reporting local structural changes. The combination of the PIFE effect with bright fluorescent dyes allows performing such measurements at the single-molecule level(1–4) or in fluorescence imaging.

In my talk, I will provide the fundamentals of PIFE, its uses in general, and in particular for studying differing questions:
(i) Do intrinsically disordered proteins (IDPs), exhibit only rapid structural transitions between unstable states, or do they also exhibit slow structural dynamics rendering them not well-folded proteins, but also not fully polymer-like ones(4–6). In this part I will summarize single-molecule PIFE measurementsin vitro using the organic dye, sulfo-Cy3, to site-specifically tag residues of the Parkinson's disease-related protein α-synuclein. The results of this part support the larger project of showing that the free monomer α-synuclein exhibits different well-defined conformational states, some of which are stable enough to act as promoters of function.
(ii) How can the phase of heterochromatin protein (HP) condensates be discerned experimentally from cellular fluorescence imaging? Here, I will summarize how can fluorescence lifetime imaging of standard fluorescent proteins can be useful, via PIFE, to sense local densities within dense phases, such as ones occurring in HP biocondensates. Using this approach, I will show that a liquid phase cannot explain HP biocondensates before
differentiation in mouse embryonic stem cells, however after initial differentiation, this changes towards a liquid phase.

References:

1. E. Ploetz, E. Lerner, F. Husada, M. Roelfs, S. Chung, J. Hohlbein, S. Weiss, T. Cordes, Förster Resonance Energy Transfer and Protein-Induced Fluorescence Enhancement as Synergetic Multi-Scale Molecular Rulers. Scientific Reports. 6, 33257–33257 (2016).
2. E. Lerner, E. Ploetz, J. Hohlbein, T. Cordes, S. Weiss, A Quantitative Theoretical Framework For Protein-Induced Fluorescence Enhancement-Förster-Type Resonance Energy Transfer (PIFE-FRET). The Journal of Physical Chemistry B. 120, 6401–6410 (2016).
3. E. Lerner, T. Cordes, A. Ingargiola, Y. Alhadid, S. Chung, X. Michalet, S. Weiss, Toward dynamic structural biology: Two decades of single-molecule Förster resonance energy transfer. Science. 359, eaan1133–eaan1133 (2018).
4. S. Zaer, E. Lerner, Utilizing Time-Resolved Protein-Induced Fluorescence Enhancement to Identify Stable Local Conformations One α-Synuclein Monomer at a Time. JoVE, e62655–e62655 (2021).
5. J. Chen, S. Zaer, P. Drori, J. Zamel, K. Joron, N. Kalisman, E. Lerner, N. V. Dokholyan, The structural heterogeneity of α-synuclein is governed by several distinct subpopulations with interconversion times slower than milliseconds. Structure (2021), doi:10.1016/j.str.2021.05.002.
6. P. D. Harris, E. Lerner, Identification and quantification of within-burst dynamics in singly labeled single- molecule fluorescence lifetime experiments. Biophysical Reports. 2, 100071 (2022).

ZOOM link: https://us02web.zoom.us/j/89236785442

A statistical physics view of swarming bacteria

Avraham Be'er, Ben Gurion University

Bacterial swarming constitutes one of the most studied examples of active matter, which is a broad class of non-equilibrium many-body system. Swarming is a complex group phenomenon during which thousands of self-propelled microscopic cells move collectively on surfaces in coherent whirls and flows, showing a variety of intricate effects. Why bacteria move that way, and how they cooperate to form this collective motion, are the two major questions that lie at the basis of my research. However, current active matter models fall short of explaining even the basic results obtained in experiments. For example, although swarming is not species-specific, some quantitative, and even qualitative results differ between mutants and species whose physics is very similar, suggesting a coupling between the physical and biological aspect of swarming. The talk intends to provide a field guide to the physics underlying bacterial swarming. I will introduce the phenomenon and describe some of the principle physical aspects of the dynamics. The conclusions stemming from the studies show the crucial contribution of physical mechanisms to this biological phenomenon. 

Laser technology has advanced rapidly from the invention of the laser in the 1960’s to the Mega-Watt lasers of the late 1980’s.  Alongside the rapid technology development comes an expectation for laser defense systems which have long been a part of science fiction literature. Nevertheless, the latter have yet to be fielded, coining the popular joke that high power laser systems have been three years away from us, for three decades.  Over the last few years, the technology has matured and the operational need for this innovative and game-changing defense system has increased making their entrance to the battlefield imminent.

This Seminar describes how these systems work and focuses on the technological breakthroughs that finally allows their realization- fiber laser power scaling via beam combining, beam focusing and pointing and real-time atmospheric turbulence disturbance correction.

Yehonathan Segev has been the head of the R&D group that specializes in Laser Systems in Rafael Advanced Defense Systems LTD since 2020. He is with the group in Rafael since 2011, after receiving a PhD from the Weizmann Institute of Science.

segevye@rafael.co.il

Zoom link: https://us02web.zoom.us/j/89236785442

Collisionless shocks around the largest structures

Uri Keshet, Ben Gurion University

Pristine collisionless shocks were recently detected around galaxy clusters - the largest objects ever to virialize, forming representative island universes on the nodes of the cosmic web. Although collisionless shocks were anticipated in the 1950s, we still have no self-consistent model for these natural particle accelerators, which boost charged particles to ultra-relativistic cosmic rays. Galaxy clusters, too, pose major open questions, with no self-consistent models for their global cooling stability, extended non-thermal emission, and unexpected spiral dynamics. I will outline our understanding, challenges, and new hints for both collisionless shock and galaxy cluster physics.

Zoom: https://us02web.zoom.us/j/89236785442

Abstract

Metallic quantum critical phenomena are believed to play a key role in many strongly correlated materials, including high temperature superconductors. Theoretically, the problem of quantum criticality in the presence of a Fermi surface has proven to be highly challenging. However, it has recently been realized that many models used to describe such systems are amenable to numerically exact solution by quantum Monte Carlo (QMC) techniques, without suffering from the fermion sign problem. I will review the status of the understanding of metallic quantum criticality, and the recent progress made by QMC simulations. The results obtained so far will be described, as well as their implications for superconductivity, non-Fermi liquid behavior, and transport in the vicinity of metallic quantum critical points. Some of the outstanding puzzles and future directions are highlighted.

An IPC event

Zoom link: https://weizmann.zoom.us/j/94885314520?pwd=Q2pra0dyS284VENiUVVhWGVTTjJFQT09

Meeting ID: 948 8531 4520

Password: 192379

Quantum gas in a box

For nearly three decades, ultracold atomic gases have been used with great success to study fundamental many-body phenomena such as Bose-Einstein condensation and superfluidity. While traditionally they were produced in harmonic electromagnetic traps and thus had inhomogeneous densities, it is now also possible to create homogeneous samples in the uniform potential of an optical box trap. Box trapping simplifies the interpretation of experimental results, provides more direct connections with theory and, in some cases, allows qualitatively new, hitherto impossible experiments. I will give an overview of our recent experiments with box-trapped three- and two-dimensional Bose gases, focusing on a series of related experiments on non-equilibrium phenomena, including phase-transition dynamics, turbulence, and equilibration of closed quantum systems.

Zoom link: https://us02web.zoom.us/j/89236785442

Non-invasive nanoscale cross-sectional XUV imaging

I will discuss nanoscale imaging in the extreme ultraviolet (XUV) spectral region using high-harmonics produced by femtosecond laser radiation. As opposed to other XUV imaging approaches, our scheme can exploit the entire high-harmonic spectrum. In fact, it is the XUV incarnation of optical coherence tomography, albeit vastly differently implemented due to the challenges of XUV optics. Thus, it is referred to as XUV coherence tomography, XCT.

A particularly relevant application of XCT for the spectral range up to 100 eV are silicon-based samples. We have demonstrated depth resolutions of 20 nm and very high sensitivities. Buried oxide layers of a thickness of a few nanometers could be detected as well as buried monolayers of graphene. It is even possible to identify the material encapsulated in silicon and determine also properties like layer roughness without destroying the sample. A unique perspective is ultrafast imaging.

ZOOM:https://us02web.zoom.us/j/89236785442&nbsp;

Elucidating the Interactions between Mechanical and (Electro)-Chemical Properties of Battery Materials

The reality of the sustainable energy policy requires higher energy density batteries for electrification of the transportation and more cost-effective batteries made of earth-abundant materials  for large-scale energy storage applications.  Diversification of battery chemistries is the key strategy to achieve the goal.  There are growing interest in beyond Li-ion battery technologies such as all-solid-state batteries, metal-air batteries and metal-ion batteries.  However, many of these battery chemistries are far away from the commercialization due to their unsatisfactory practical electrochemical performance. Lifetime and performance of the batteries depends on the (electro)-chemo-mechanical instabilities in the materials during battery operation. Elucidating the coupling between electrochemistry and mechanics of electrodes beyond Li-ion batteries is critical to design materials suitable for battery chemistries. In this talk, I will address provide examples for (electro)-chemo-mechanical instabilities in different battery chemistries.

Na-ion batteries have attracted attention in the search for cost-effective batteries with a minimum sacrifice on the performance for large-scale energy storage applications. However, the physical and chemical properties of Na is intrinsically different than Li-ions.  Lack of insight into the influence of alkali ions on the interfacial dynamics and mechanical degradations of electrodes limits the design of novel materials.  For high energy demanding applications such as electrical planes and vehicles, Li-O₂ batteries are promising candidates because their theoretical energy density is almost ten times higher than the Li-ion batteries. However, they suffer from severe interfacial instabilities associated with sluggish kinetics of the redox reactions and the insulating nature of the reduced oxygen species on the cathode surface. Solid electrolytes offer a promising way to increase the energy density by allowing the utilization of Li metal as an anode material for electrical vehicle applications. Despite the growing interest in solid electrolyte-based Li metal batteries, the utilization of the technology is still hindered by solid-solid interactions and chemo-mechanical instabilities in all-solid-state batteries.

In this presentation, I will first describe in situ curvature and digital image correlation measurement techniques to probe the electro-chemo-mechanical responses of battery materials. Second, I will present the effects of larger charge carrier ions (Na-ion and K-ion) on the chemo-mechanical behavior of battery electrodes^1,2.  Third, I will present the role of electrolyte chemistry on the reaction dynamics on the Li-O₂ battery cathodes. In particular, I will discuss the linkage between mechanical deformations and electrochemical behavior in the Li-O₂ battery cathodes³. Last, I will present the coupling between overpotentials and interfacial deformations in all-solid-state batteries⁴.

References:

1. B. Ozdogru & Ö. Ö. Çapraz et al., ACS Nano Letters, 21, 18, 7579–7586, 2021.
2. B. Ozdogru & Ö. Ö. Çapraz et al., Electrochemical Science Advances, e2100106, 2021
3. H. Dykes & Ö. Ö. Çapraz et al., J. Electrochem. Soc., 168, 110551, 2021.
4. B. Ozdogru & Ö. Ö. Çapraz et al., ACS Applied Energy Materials, In Press, 2022.

Biography

Dr. Çapraz received his Ph.D. degree in Chemical and Biochemical Engineering with a Mechanical Engineering minor from Iowa State University in 2014. He was a post-doctoral researcher in the Beckman Institute at the University of Illinois at Urbana-Champaign until 2018. Currently, he is an assistant professor in the School of Chemical Engineering at Oklahoma State University since Fall 2018. His research focuses on electrochemical energy storage and conversion devices, in situ chemo-mechanical characterization techniques, and advanced materials. His research group is investigating chemical and mechanical failure modes in all-solid-state batteries, Li-air batteries, alkali metal-ion batteries, and pseudo capacitors. His research has been supported by various agencies such as National Science Foundation, the Department of Energy, Binational Science Foundation, NASA, Air Force, and Lee Wentz Foundation. He received prestigious NSF CAREER award and BSF Young Investigator Start-up award.

Cancelled

Zoom link: https://us02web.zoom.us/j/89236785442

Haim Beidenkopf, Weizmann Institute

Abstract

A small change in the crystal structure of a material can completely modify its electronic properties. This is the case in the transition metal dichalcogenide TaS2 where a slight rotation of the sulphur atoms from the trigonal prismatic 1H structure to the octahedral 1T varies it from a superconductor to a Mott insulator possibly hosting a spin liquid state. We have studied 4Hb-TaS2 that interleaves the 1T and 1H polytypes. This has allowed us to investigate using scanning tunneling spectroscopy the fate of a Mott insulator when coupled to a metal and the superconducting phase that results from sandwiching it with Mott insulating layers. In the former we find a quantum phase transition that can be induced by the STM tip, electric field and temperature which possibly signifies the onset of correlations among Anderson impurities (or of a Kondo lattice). In the latter we identify a topological nodal superconducting state which we attribute to interaction-promoted inter-orbital pairing.

Please note! We are back in room 301!

Zoom:https://us02web.zoom.us/j/89236785442

Suppression of Electrode Material Degradation by Using Surface Modifications Techniques

Powering most currently used portable devices, batteries ushered electronics into a new era of mobile energy, directly supporting and influencing our daily lives. However, the ever-increasing demand for energy storage devices with improved performances and is challenging the scientific community to develop new chemistries and morphologies of electrode materials (EM) to move beyond current technology toward electrochemical storage devices with higher energy density, superior power performance and significantly extended stability.

Understanding fundamental degradation mechanisms of EMs, and their mitigation strategies, are challenged by constraints of the liquid electrolyte environment and the complexity of electrode/electrolyte interphase formation, namely the solid electrolyte interphase (SEI) layer which forms, grows, and changes (on the electrode interface) with battery usage.  Accordingly, the research community is increasingly seeking new pathways to understand and control battery degradation, including new diagnostic and characterization methods as well as mitigation strategies (e.g., electrode surface treatments, electrolyte additives and artificial SEI layers).

In my talk I will demonstrate how surface modification of EMs, significantly suppress the degradation of the battery components (e.g. electrodes, and electrolyte) and facilitates long-term stability of the electrochemical device.

I will demonstrate how in our lab, we modify the surface of the EMs by either thin protection layer applied on its interface (using atomic/molecular layer deposition- M/ALD), or by surface reduction of high voltage cathode materials. I will farther show how we monitor In-Operando the degradation of the electrode\electrolyte interface using online electrochemical mass spectroscopy (OEMS), and will demonstrate the efficacy of our coating strategy in suppressing the degradation pathway of the Ems.

Lecture in the IPC series

Priyamvada Natarajan, Yale University

ZOOM LINK 

LENSING PROBES OF THE COLD DARK MATTER PARADIGM

Abstract

Gravitational lensing by clusters of galaxies offers a powerful probe of theories of structure formation. The standard paradigm of a cold dark matter dominated Universe provides concrete predictions for  small-scale substructure properties including their abundance, radial distribution and lensing efficiency. I present recent exciting result that confront observationally inferred quantities that map dark matter on small-scales with predictions of cosmological simulations. The power and prospects for stress-testing the cold dark matter paradigm with lensing data will be discussed. With the upcoming data deluge new stringent tests of dark matter will become feasible and viable.

ZOOM:https://us02web.zoom.us/j/89236785442

Complex molecules in space: How do they form and how do they cool down?

Although mostly empty and cold, the interstellar medium (ISM) is beaming with molecules, with over 200 different species already identified. The goals of laboratory astrophysics are to measure properties of molecules in conditions similar to those of the ISM in order to identify new species and understand the processes by which they are formed, destroyed, and the evolution of their internal energy. Recent years have seen the comissioning of the cryogenic storage ring (CSR), which is quickly establishing itself as the most advanced tool of laboratory astrophysics. In this talk the CSR will be introduced, and  our recent measurements on the cooling of symmetric molecules in the ISM will be discussed. In addition, our works on the intra-cluster bond formation will be presented, and their implication as possible mechanisms for formation of complex molecules in the ISM.

ZOOM: https://us02web.zoom.us/j/89236785442

Zoom Link: https://us02web.zoom.us/j/89236785442

Quantum sensing with unlimited optical bandwidth

Avi Pe’er, Physics department and QUEST center for quantum technology, Bar Ilan University, Ramat Gan 52900 ISRAEL

Squeezed light is a major resource for quantum interferometric sensing below the shot-noise limit. However, standard squeezed interferometry methods suffer from two severe limitations: First, the detection bandwidth of squeezing-enhanced interferometry is inherently narrow because of the slow response (MHz to GHz) of photodetectors, which prevents efficient utilization of the optical bandwidth (tens of THz and more) for quantum applications; and second, current quantum sensing requires near ideal photo-detectors with unity efficiency, prohibiting applications, where ideal detection is not available. To overcome these limitations and harvest the orders-of-magnitude enhancement of the sensing throughput, a paradigm shift is required in terms of broadband quantum sources, detection schemes, and interferometric design.
I will present a set of new methods for sub-shot-noise sensing, based on nonlinear interferometry, which overcome these limitations. By placing the phase object in question between two parametric amplifiers in series, the first amplifier generates broadband squeezed light to interrogate the object and the second amplifier acts as an ideal broadband quantum detector to measure the object’s response. This technique is robust to detection inefficiency and provides an unprecedented optical bandwidth for quantum measurement, exceeding the possibilities of photodetectors by several orders of magnitude.
I will discuss in detail two specific examples of ultra broadband parametric-homodyne measurement [1] and of squeezing-enhanced Raman spectroscopy [2].

References:
[1] Y. Shaked, Y. Michael, R. Vered, L. Bello, M. Rosenbluh and A. Pe’er, “Lifting the Bandwidth Limit of Optical Homodyne Measurement”, Nature Communications 9, 609 (2018).
[2] Y. Michael, L. Bello, M. Rosenbluh, and A. Pe'er, “Squeezing-enhanced Raman Spectroscopy”,  npj Quantum Information 5, 81 (2019).

[3] L. Bello, Y. Michael, M. Rosenbluh, E. Cohen and A. Pe’er, “Broadband complex two-mode quadratures for quantum optics”, Optics Express 29, 41282 (2021)

Zoom link: https://weizmann.zoom.us/j/92614035030?pwd=Q251T28xang4Qkg3Y3NPbHIyT2sr…

Black-Hole Entropy: its Key Role in the 2nd Law of Thermodynamics

Observational cosmology reveals the presence, in the current universe, of supermassive black holes whose total entropy should easily dominate that of the entire universe, according to the fundamental Bekenstein-Hawking formula. But this was not always the case. At the time of the emission of the microwave background radiation, some 380,000 years following the Big Bang, the entropy contribution from gravitational effects was extremely tiny, that in the matter having been extremely close to the maximum that it could have been. For some reason, at the Big bang itself, gravitational degrees of freedom were enormously suppressed, thereby allowing the 2nd Law of Thermodynamics to operate, as gravitational degrees relentlessly became activated, leading to their domination in the black holes currently observed.
 
But what about the remote future? We must expect that this trend will continue, even to the final evaporation of the black holes in an ever exponentially expanding universe. A seeming paradox lies behind this picture, in the extreme difference between the singularity structure at the Big Bang, where gravitational degrees of freedom are strangely suppressed, and the very opposite in the singularities in black holes, whose singularities appear to have the maximum entropy possible. It is hard to see how any direct quantization of gravity can resolve this gross time-asymmetric puzzle. Indeed, it can be argued that any quantization of gravity cannot resolve this issue without, apparently, an accompanying “gravitization” of quantum theory, in which the fundamental “measurement problem” of quantum mechanics is also resolved. Such a theory is currently lacking, but various experiments are now under serious consideration, to test this very basic idea.
 
Nevertheless, a deeper understanding of the special nature of the Big Bang can be illuminated by examining it from the perspective of conformal geometry, according to which the Big-Bang singularity becomes non-singular, this being quite different from the situation arising from the singularities in black holes. In conformal geometry, big and small become equivalent, which can only hold for a singularity of the type we seem to find at the Big Bang. This situation is also relevant in relating the extremely hot and dense Big Bang to the extremely cold and rarefied remote future of a previous “cosmic aeon”, leading to the picture of conformal cyclic cosmology (CCC) according to which our Big Bang is viewed as the conformally continued remote future of a previous cosmic aeon. It turns out that there are now certain strong observational signals, providing some remarkable support for this highly non-intuitive but mathematically consistent CCC picture.

ZOOM link:https://us02web.zoom.us/j/89236785442

Order from the disorder

Roy Beck

Tel Aviv University, Tel Aviv, Israel

In this colloquium, I will review the recent trends where statistical mechanics ideas transform our understanding of molecular biology. I will also present new peptide amphiphiles composed of an intrinsically disordered peptide conjugated to variants of hydrophobic domains. These molecules, termed intrinsically disordered peptide amphiphiles, exhibit a sharp pH-induced micellar phase transition from low-dispersity spheres to extremely elongated worm-like micelles. I will present various experimental characterizations of the transition and propose a theoretical model to describe the pH response, routed on the weak interactions between disordered proteins. I will also show the potential of the shape transition to serve as a mechanism for the design of a cargo hold-and-release application. Such amphiphilic systems demonstrate the power of tailoring the interactions between disordered peptides for various stimuli-responsive biomedical applications.

Zoom link: https://us02web.zoom.us/j/89236785442

How low can electronic resistance go?

Ady Stern (Weizmann)

Electronic resistance is a fundamental notion both in condensed matter physics and in everyday life, where it is a source of heating caused by electronic currents. Typically, resistance originates from electrons scattering off impurities. However, even a perfectly clean system harbors a resistance, inversely proportional to the number of its conduction channels. Recent theories have shown that scattering of the flowing electrons off one another reduces this resistance, raising the question of its lower bound. Here we show that for a fixed number of channels the resistance may be practically eliminated, and give a transparent physical picture of this elimination.  

In this talk, we will explore one of the leading technologies for quantum computing: superconducting circuits. This is the technology used by Google, IBM and many others to build their quantum computers. We will review the underlying principles and the current status of this technology. We will then discuss our approach of encoding quantum information in superconducting resonators instead of in two-level systems. Resonator qubits hold promise to achieve coherence times far beyond the current state of the art, and offer new ways to error-correct the quantum information. We will present preliminary data of our progress towards this goal.

zoom: https://us02web.zoom.us/j/89236785442

Physical applications of infinite ergodic theory

Eli Barkai

Fermi pointed out that the Hydrogen atom in a thermal setting is unstable, as the canonical partition function of this simple system diverges. We show how non-normalised Boltzmann Gibbs measure can still yield statistical averages and thermodynamic properties of physical observables, exploiting a model of Langevin dynamics of a single Brownian particle in an asymptotically flat potential [1]. The ergodic theory of such systems is known in  mathematics as infinite (non-normalisable) ergodic theory, a framework that is widely applicable from laser cooled gases to non-linear systems.

[1] E. Aghion, D. A. Kessler, and E. Barkai , Non-normalizable Boltzmann-Gibbs statistics to infinite-ergodic theory, Phys. Rev. Lett. 122, 010601 (2019)
 

Quantum simulators: from the Fermi Hubbard model to quantum assisted NMR inference

I will review recent progress of the optical lattice emulators of the Fermi Hubbard model. The new feature of these experiments is availability of snapshots of many-body states with single particle resolution. I will discuss new insight from these experiments on the properties of magnetic polarons in antiferromagnetic Mott insulators. I will also discuss the idea of using quantum simulators to perform inference of NMR spectra for biological molecules. Practical aspects of realizing this hybrid quantum-classical algorithm on currently available experimental platforms will be reviewed.

https://weizmann.zoom.us/j/92614035030?pwd=Q251T28xang4Qkg3Y3NPbHIyT2srdz09

Meeting ID: 926 1403 5030

Password:  508567

Zoom: https://us02web.zoom.us/j/89236785442

When electrons are injected through a chiral molecule, the resulting current may become spin polarized. This effect, known as the chirality-induced spin-selectivity (CISS) effect, has been suggested to emerge due to the interplay between spin–orbit interactions and the chirality within the molecule. However, such explanations require unrealistically large values for the molecular spin–orbit interaction without any physical justification. Put simply, to date, the physical origin of  the CISS effect is unknown. 
Here, we present a theory for the CISS effect based on the interplay between spin–orbit interactions in the electrode, the chirality of the molecule (which induces a solenoid field), and spin-transfer torque at the molecule–electrode interface. Using a mean-field calculation with simple models for the molecular junction, we show that our phenomenological theory can qualitatively account for all key experimental observations, most importantly the magnitude of the CISS with realistic parameters. We also provide a set of predictions which can be readily tested experimentally, and show recent data to corroborate these predictions. 

S. Alwan & Y. Dubi, J. Am. Chem. Soc. 2021, 143, 35, 14235–14241.

Zoom:  https://us02web.zoom.us/j/89236785442

Symmetry breaking in the formation of chiral nanocrystals

Gil Markovich

School of Chemistry, Tel Aviv University

Chirality (lack of mirror symmetry) is a fundamental property of biomolecules (amino acids, proteins, nucleic acids, DNA, sugars), and an essential part of their complex structures. Remarkably, almost all such biomolecules are of a single handedness (homochirality), and the reason for this symmetry breaking is one of the key questions in understanding the origin of life.

We are interested in symmetry breaking in inorganic compounds. Many inorganic compounds crystallize in chiral space group, such as quartz, for example. Our group has been studying the breaking of left-right symmetry in the formation of nanocrystals of such compounds. We have shown, that using small chiral bio-molecules which interact with the crystals’ building blocks, it is possible to achieve such symmetry break. In particular, we have been working with the chiral TbPO₄×H₂O nanocrystals, and have shown that their handedness can be controlled by preparing the nanocrystals in the presence of certain natural chiral molecules, such as tartaric acid. We use circularly polarized luminescence measurements of Eu³⁺ dopant ions in the nanocrystals to follow the handedness and enantiomeric purity of the produced nanocrystals.[1] Using single particle circularly polarized luminescence microscopy we were able to determine the handedness of individual nanocrystals and confirmed that we obtain a single mirror image (enantiomer) of the terbium phosphate nanocrystals when prepared with tartaric acid molecules.[2] We also discovered that at low enough synthesis temperatures the nanocrystals (almost-) spontaneously, randomly break symmetry (in the presence of minute amounts of chiral material) and propose a model for the symmetry breaking effects in the nanocrystal formation. This kind of super-sensitive symmetry-breaking effects could serve as models for the riddle of homochirality of biomolecules at the origin of life.

References

1. U. Hananel, A. Ben-Moshe, H. Diamant, G. Markovich, Proc. Natl. Acad. Sci. USA 116, 11159-11164 (2019)
2. E. Vinegrad, U. Hananel, G. Markovich, O. Cheshnovsky, ACS Nano 13, 601–608 (2019).

The latest IceCube data suggest that the all-flavor cosmic neutrino flux may be as large as 10⁻⁷ GeV/cm²/s/sr around 30 TeV. We show that, if astrophysical sources of the TeV-PeV neutrinos are transparent to gamma rays with respect to two-photon annihilation, a large fraction of the isotropic diffuse -ray background should originate from hadronic emission of such sources, independently of the production mechanism. Strong tensions with the diffuse gamma-ray data are unavoidable especially in hadronuclear (pp) scenarios. We further show that, if the IceCube neutrinos have a photohadronic (p) origin, the sources are expected to be opaque to 1–100 GeV gamma rays. With these general multimessenger arguments, we find that the latest data may indicate a population of CR accelerators hidden in GeV-TeV gamma rays. In this talk I discuss the possibility that neutrinos may come from jets of collapsing massive stars which fail to break out of the stellar envelope, and for this reason they are known as choked jets, or choked Gamma-Ray Bursts (GRBs). In this talk, I will show the neutrino flux and spectrum expected from these sources, focusing on Type II SNe. I will provide predictions of expected event rates for operating neutrino telescopes, such as ANTARES and IceCube, as well as for the future generation telescope KM3NeT. I will show that for GRB energies channelled into protons spanning between ~ 10⁵¹-10⁵³ erg, choked GRBs may substantially contribute to the observed astrophysical neutrino flux, if their local rate is ~ 80-1 Gpc^-3yr^-1 respectively.

Since these sources are hidden in the gamma-rays, searches for x-ray and UV-ray counterparts from these sources are encouraged.

Zoom: https://us02web.zoom.us/j/89236785442

The three-body problem is arguably the oldest open question in astrophysics and has resisted a general analytic solution for centuries. Various forms of perturbation theory provide solutions in portions of parameter space, but only where hierarchies of masses and/or separations exist. Numerical integrations show that bound, non-hierarchical triple systems of Newtonian point particles will almost always disintegrate into a single escaping star and a stable bound binary, but the chaotic nature of the three-body problem prevents the derivation of analytic formulae that deterministically map initial conditions to final outcomes. Chaos, however, also motivates the assumption of ergodicity. I will present a new statistical solution to the non-hierarchical three-body problem that is derived using the ergodic hypothesis and that provides closed-form distributions of outcomes (for example, binary orbital elements) when given the conserved integrals of motion. We compare our outcome distributions to large ensembles of numerical three-body integrations and find good agreement, so long as we restrict ourselves to "resonant" encounters (the roughly 50% of scatterings that undergo chaotic evolution). In analysing our scattering experiments, we identify "scrambles" (periods of time in which no pairwise binaries exist) as the key dynamical state that ergodicizes a non-hierarchical triple system. I will briefly discuss how the generally super-thermal distributions of survivor binary eccentricity that we predict have applications to many astrophysical scenarios. For example, non-hierarchical triple systems produced dynamically in dense star clusters are a primary formation channel for black-hole mergers, but the rates and properties of the resulting gravitational waves depend on the distribution of post-disintegration eccentricities.

[ZOOM link for hybrid participation - https://us02web.zoom.us/j/89236785442]

Quantum Dot Physics Using Atomic Defects in Ultrathin Tunnel Barriers

Hadar Steinberg

Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel

Quantum dots (QDs) are conducting regions which can localize few charge carriers, and where the energy spectrum is dominated by Coulomb repulsion. QDs can be as large as few hundreds of nanometers, or as small as a single molecules, their sizes depending on their physical realization – whether in two-dimensional materials, nanowires, molecular systems.

In my talk I will describe our work on a new type of an atomically-sized QD, realized in defects residing in ultrathin two-dimensional insulators. These defect-dots are found in layered materials such as hexagonal Boron Nitride (hBN), which we study by their assembly into stacked devices. By using graphene electrodes, we able to electronically couple to the QD, while allowing the QD energy to be externally tuned exploiting the penetration of electric field through graphene.

A consequence of the structure of our devices is that the defect QDs are placed at atomic distance to the conductors on both sides. I will show how the presence of such energy-tunable, atomically sized QDs at nanometer proximity to other conducting systems opens new opportunities for sensitive measurements, including use of QDs as highly sensitive spectrometers [1], or as single electron transistors, unique in their sensitivity to local electric fields at the nanometer scale [2]. I will discuss our future prospects of using defect QDs as quantum sensors.

References

1. Devidas, T.R., I. Keren, and H. Steinberg, Spectroscopy of NbSe₂ Using Energy-Tunable Defect-Embedded Quantum Dots. Nano Letters, 2021. 21(16): p. 6931-6937.

2. Keren, I., et al., Quantum-dot assisted spectroscopy of degeneracy-lifted Landau levels in graphene. Nature Communications, 2020. 11(1): p. 3408.

https://us02web.zoom.us/j/89236785442

Zoom Link,  Meeting ID: 942 2865 5001, Password: 802363

The solution of the two-body problem in General Relativity is playing a crucial role in observing gravitational waves from binary systems composed of black holes and neutron stars, and inferring their astrophysical, cosmological and gravitational properties. After reviewing the synergistic approach that successfully combines analytical and numerical relativity to produce highly accurate waveform models, I will discuss the most compelling and puzzling findings from the most recent LIGO-Virgo observing run.

Zoom Link     Meeting ID: 445 992 8099

The Kepler space mission observed more than 150,000 stars continuously for more than four years, producing unprecedentedly precise light curves.

The Kepler data enabled detecting thousands of stars with transit-like light curves, many of which are circled by more than one planet. The talk will review how Kepler has advanced our understanding of multiple exo-planet systems. This includes the systems’ architecture, obtained by evidence for dynamical interaction between the planets, and the discovery of circumbinary planets.

NOTICE: This is a hybrid colloquium, given from the Physics Auditorium, and broadcasted also via Zoom

Zoom link: https://us02web.zoom.us/j/4459928099

Title: The Hall effect:  what moves in a metal or a superconductor?

Speaker: Assa Auerbach, Department of Physics, Technion

Abstract:

The Hall resistivity has long been used to identify the mobile charge carriers in metals. 
However, transport theory has failed to explain several intriguing  ‘’Hall anomalies’’ in strongly correlated metals, superconductors, and thermal Hall effect in insulators.
Recent advances by our group include new formulas for the Hall coefficient, and a revised theory of flux flow in superconductors, which help us understand  the ‘’moving parts’’  in transport currents of these systems.

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I will explain how precision measurements and correlations within the Cosmic Microwave Background, Large Scale Galactic Structure and 21-cm Cosmology can probe the fundamental physics of extremely heavy particles, orders of magnitude beyond the reach of terrestrial particle experiments such as the CERN Large Hadron Collider. Intuitively, the production of heavy particles is due to the high “Hawking Temperature” during the universe’s “growth spurt” of Cosmic Inflation. This mechanism is generalized and applied to showing how we can experimentally test our most ambitious gauge-Higgs and higher-dimensional theories, such as (Orbifold) Grand Unification, Dark Sectors, and the Standard Model itself.

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Quantum materials offer particularly appealing opportunities for the implementation of on-demand quantum phases.  This class of materials host interacting many-body electronic systems featuring an intricate interplay of topology, reduced dimensionality, and strong correlations that leads to the emergence of “quantum matter’’ exhibiting macroscopically observable quantum effects over a vast range of length and energy scales. Central to the nano-optical exploration of quantum materials is the notion of polaritons: hybrid light-matter modes that are omnipresent in polarizable media. Infrared nano-optics allows one to directly image polaritonic waves yielding rich insights into the electronic phenomena of the host material supporting polaritons. We utilized this novel general approach to investigate the physics of on-demand hyperbolic exciton-polaritons in a prototypical atomically layered van der Waals semiconductor WSe2 and of infrared non-reciprocity in a current carrying graphene device[3].

[1] D. N. Basov, Ana Asenjo-Garcia, P. J. Schuck, X. Zhu & Angel Rubio, “Polariton panorama” Nanophotonics 10, 549 (2021) https://infrared.cni.columbia.edu/research/polariton-panorama-2-2/

[2] A. J. Sternbach, S. Chae, S. Latini, A. A. Rikhter, Y. Shao, B. Li, D. Rhodes, B. Kim, P. J. Schuck, X. Xu, X.-Y. Zhu, R. D. Averitt, J. Hone, M. M. Fogler, A. Rubio, and D. N. Basov, “Programmable hyperbolic polaritons in van der Waals semiconductors” Science 371, 617 (2021).

[3] Y. Dong, L. Xiong, I.Y. Phinney, Z. Sun, R. Jing, A.S. McLeod, S. Zhang, S. Liu, F. L. Ruta, H. Gao, Z. Dong, R. Pan, J. H. Edgar, P. Jarillo-Herrero, L.S. Levitov, A.J. Millis, M. M. Fogler, D.A. Bandurin, D.N. Basov “Fizeau Drag in Graphene Plasmonics” to appear in Nature (2021); arXiv:2103.10831

Electrostatic manipulation of High-Tc superconductivity: the hammer and the scalpel

Javier E. Villegas*

Unité Mixte de Physique, CNRS, Thales, Université Paris Saclay, Palaiseau, France

Field-effect devices based on oxide superconductors constitute an interesting playground to investigate a rich variety of physical phenomena. They also bear much potential for novel functionalities. To illustrate that, I will show transport experiments on junctions between oxide-superconductors and non-superconducting materials, in which the conductance is modulated by electric field effects via different mechanisms.

First I will briefly discuss the observation of quasiparticle tunnel electroresistance in superconducting junctions. The term “tunnel electroresistance” was formerly coined to describe a non-volatile resistive switching observed in ferroelectric tunnel junctions upon application of a voltage pulse. This effect, which has opened the door to a new class of memories, can be explained by subtle mechanisms related to the nonvolatile reversal of the ferroelectric polarization. Our experiments with superconducting electrodes demonstrate that the same electroresistance can be produced by a more prosaic mechanism: oxygen electro-migration and the resulting modification of the electrodes’ ground-state. Furthermore, we demonstrate that the electroresistance is orders-of-magnitude stronger for quasiparticles than for normal electrons^1,2

Second, I will discuss the electrostatic manipulation of the proximity effect in cuprate superconductor/graphene junctions ³Here, the underlying mechanism is the controlled variation the graphene’s Fermi vector through electrical gating. This allows tuning electron interferences that modulate the Andreev reflection at the superconductor/graphene interface. Furthermore, a different type of interferences –this time controlled by the bias voltage– are observed which are due to geometrical resonances and the coherent propagation of electron/hole pairs in graphene.⁴

1.        Bégon-Lours et al. Phys. Rev. Mater. 2, 084405 (2018).

2.        Rouco et al. Nat. Commun. 11, 1 (2020).

3.        Perconte et al. Nat. Phys. 14, 25 (2018).

4.        Perconte et al. Phys. Rev. Lett. 125, 087002 (2020).

*In collaboration with: D. Perconte, V. Rouco, C. Ulysse, D. Bercioux, J. Trastoy, A. Sander, P. R. Kidambi, S. Hofmann, B. Dlubak, P. Seneor, F. S. Bergeret, R. El Hage, J. Grandal, J. Briatico, S. Collin, K. Bouzehouane, A.I. Buzdin, G. Singh, N. Bergeal, C. Feuillet-Palma, J. Lesueur, M. Varela, and J. Santamaría

Work supported by the ERC grant Nº 647100, French ANR grant ANR-15-CE24-0008-01 and COST “Nanoscale Coherent Hybrid Devices For Superconducting Quantum Technologies” - Action CA16218.

Talk will be via ZOOM: https://us02web.zoom.us/j/8866328706 

:Zoom link, Meeting ID: 951 7512 2285

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This talk will tell the story of a journey from earth to the moon, from fantasy to reality. The story of three young engineers who chose to challenge the exclusive club of superpowers in deep space travel, and found a whole nation joining them along the way. It’s a story of hope and heartbreak, of incredible accomplishments beside (nearly) impossible difficulties. It’s the story of children that fueled a spaceship with their hopes and dreams and sent a clear message: “Shoot for the moon and follow your dreams!”

Zoom Link:  https://us02web.zoom.us/j/4459928099
Meeting ID: 445 992 8099

Kaposi's sarcoma, the most common AIDS-associated malignancy, is caused by a human herpesvirus, KSHV. Rare types of lymphoproliferative diseases are also arising from KSHV infection. Nevertheless, the details of KSHV infection and pathogenesis remain unclear. HSV-1, another human herpesvirus, is a common infectious agent that occurs worldwide and infects humans of all ages. The outcome of HSV-1 infection includes a wide variety of clinical manifestations, ranging from asymptomatic infection to oral cold sores and severe encephalitis.

Our research deals with basic questions related to these viruses that could potentially lead to the discovery of novel approaches for antiviral interventions. Three main topics will be presented in the seminar, including: Tracking virus infection by using recombinant viruses expressing fluorescent proteins and fluorescently-tagged viral proteins; Generation of virions lacking nucleic acid and characterization of their docking to the nuclear pores; and inhibition of virus infection by using composite nanoparticles that block the attachment of virions to host cells.

Zoom Meeting ID: 951 7512 2285

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Many biological systems use the beating of cilia either to propel themselves or to induce fluid flow around them. Recent experiments in the group of Pascal Martin at Institute Curie study the beating of self-assembled actin bundles anchored on a solid surface induced by myosin motors, which can be considered as artificial cilia. In addition to the beating pattern of each cilium, the experiment images a wave of myosin motors along the cilium.

Classical theories describe the beating cilium as a bending slender beam immersed in a viscous fluid dissipation being due to the external hydrodynamic drag of the viscous fluid. The beating is created by an active mechanism internal to the cilium and due to molecular motors.

I will present in this talk a very generic theory of cilia beating that includes the various types of external and internal dissipation and of active forces propelling the cilium and that explicitly considers the molecular motor distribution along the cilium. The theory is based on the entropy production on the cilium  and the various dissipative forces are obtained from Onsager force-flux relations. The active forces are related to myosin motor densities along the cilium obtained from binding and unbinding kinetics for the motors.

A simple version of this theory in two dimensions provides a quantitative description of the experiments on artificial cilia done in the group of Pascal Martin.

Link to recording

Quantum computing holds the promise to solve specific computational problems much faster than any known classical algorithm. Current quantum computers are, however, too small and too noisy to perform useful calculations. In this talk I will follow a different route and show how to use these systems to study fundamental physical questions, and specifically those related to the dynamics of many-body quantum systems. I will focus on two specific applications of quantum computers on the cloud: the demonstration of the topological property of spin models [1] and the realization of a quantum system with long range interactions [2]. These works raise new basic questions concerning the effects of classical noise on quantum states of matter, and provide a useful benchmark for actual quantum computers.

1.         Daniel Azses, Rafael Haenel, Yehuda Naveh, Robert Raussendorf, Eran Sela, Emanuele G. Dalla Torre, Identification of symmetry-protected topological states on noisy quantum computers, Physical Review Letters 125, 120502 (2020)

2.         Mor M. Roses, Haggai Landa, Emanuele G. Dalla Torre, Simulating long-range hopping with periodically-driven superconducting qubits, https://arxiv.org/abs/2102.09590

Zoom Details:  Meeting ID: 951 7512 2285,    Password: 071333

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The ALPHA experiment at the Antiproton Decelerator is unique in its combined ability to produce, trap, and study atoms of antihydrogen - the simplest anti-atom. The Standard Model requires that hydrogen and antihydrogen have the same spectrum.  Transition frequencies in hydrogen can be measured with precisions of order 10-15.  The precision in antihydrogen at ALPHA is now of order 10-12, making atom/anti-atom comparisons among the most precise, direct tests of fundamental symmetries in Nature.  Also of fundamental interest is the gravitational behaviour of antimatter, the study of which is the goal of the new ALPHA-g experiment. I will discuss the decades of development necessary to achieve the latest groundbreaking results in ALPHA. Among the latter is the demonstration of laser cooling of antihydrogen, published last week in Nature.  I will then consider the future of spectroscopy and gravitational studies with antihydrogen in the era of CERN’s brand-new ELENA facility, which will deliver antiprotons to us in August of 2021.

Link to recording of the talk

ABSTRACT:

The first gravitational wave detection of a neutron star merger, GW170817, opened the era of multi-messenger gravitational wave-electromagnetic (GW-EM) astrophysics. It is a special event in many levels and its follow-up campaign is probably the largest coordinated observational effort in astrophysics dedicated to a single event. It offers an unprecedented data set, and although it is only a single event, it provides remarkable insights about fundamental physics and astrophysics and revolutionizes our knowledge on neutron star mergers. In my talk, I will give an overview of the main lessons from this event.

Udi (Ehud) Nakar is a Professor of Astrophysics in Tel Aviv University since 2009. His main field of interest is high-energy astrophysics and in particular the physical processes that are active in sources of high energy radiation, cosmic-rays, neutrinos and gravitational waves. His studies combine high-performance computing numerical simulations and analytic work. He received, among other, the IPS prize for young scientists and the ERC starting grant. Ehud is a member of the Israel Young Academy.

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I will show how an in-depth description of the basic principles of diffraction-unlimited fluorescence microscopy (nanoscopy) [1-3] has spawned a new powerful superresolution concept, namely MINFLUX nanoscopy [4]. MINFLUX utilizes a local excitation intensity minimum (of a doughnut or a standing wave) that is targeted like a probe in order to localize the fluorescent molecule to be registered. In combination with single-molecule switching for sequential registration, MINFLUX [4-6] has obtained the ultimate (super)resolution: the size of a molecule. MINFLUX nanoscopy, providing 1–3 nanometer resolution in fixed and living cells, is presently being established for routine fluorescence imaging at the highest, molecular-size resolution levels. Relying on fewer detected photons than popular camera-based localization, MINFLUX nanoscopy is poised to open a new chapter in the imaging of protein complexes and distributions in fixed and living cells.

[1]  Hell, S.W., Wichmann, J. Breaking the diffraction resolution limit by stimulated emission: stimulated-emission-  depletion fluorescence microscopy. Opt. Lett. 19, 780-782 (1994).

[2]  Hell, S.W. Far-Field Optical Nanoscopy. Science 316, 1153-1158 (2007).

[3]  Hell, S.W. Microscopy and its focal switch. Nat. Methods 6, 24-32 (2009).

[4]   Balzarotti, F., Eilers, Y., Gwosch, K. C., Gynnå, A. H., Westphal, V., Stefani, F. D., Elf, J., Hell, S.W. Nanometer resolution   imaging and tracking of fluorescent molecules with minimal photon fluxes. Science 355, 606-612 (2017).

[5]  Eilers, Y., Ta, H., Gwosch, K. C., Balzarotti, F., Hell, S. W. MINFLUX monitors rapid molecular jumps with superior   spatiotemporal resolution. PNAS 115, 6117-6122 (2018).

[6]  Gwosch, K. C., Pape, J. K., Balzarotti, F., Hoess, P., Ellenberg, J., Ries, J., Hell, S. W. MINFLUX nanoscopy delivers   multicolor nanometer 3D-resolution in (living) cells.  (bioRxiv, doi: https://doi.org/10.1101/734251)

Title: Interactions of light and sound waves in optical fibers and photonic integrated circuits

Prof. Avi Zadok, Faculty of Engineering and Institute for Nano-Technology and Advanced Materials, Bar-Ilan University. 

Email: Avinoam.Zadok@biu.ac.il 

Link to recording

Abstract: The propagation of optical waves in media exerts forces that may stimulate the oscillations of acoustic waves. The acoustic wave, in turn, can scatter and modulate light. The interplay of the two wave phenomena has drawn the attention of researchers since the 1880's. Our group is studying light-and-sound interactions in standard optical fibers and in silicon-photonic integrated circuits. In this seminar, I will present some of our latest, yet unpublished results of the last year: Inter-polarization scattering in standard and polarization-maintaining fibers, optical stimulation of acoustic vortex beams, and integrated microwave-photonic filters with arbitrary transfer functions and few-MHz linewidths. 

Very short bio: Prof. Avi Zadok joined the Faculty of Engineering, Bar-Ilan University in 2009. His research interests include fiber optics, nonlinear optics, opto-mechanics, and photonic integrated circuits. Prof. Zadok was the Chair of the Israel Young Academy for the year 2019-2020. 

This is part of the Israel Physics Colloquium

Please observe start time 16:00 PM

Discovering New Physics with Cosmological Data Sets

Measurements of the Cosmic Microwave Background and the large-scale structure of the universe have made it possible to determine with great precision the universe's inventory, as well as properties of its initial conditions. However, there are profound questions that remain unanswered. Cosmological observations and galaxy dynamics seem to imply that 84% of all matter in the universe is composed of dark matter, which is not accounted for by the Standard Model of particles. The particle nature of dark matter is one of the most intriguing puzzles of our time. The wealth of knowledge which is and will soon be available from cosmological surveys will reveal new information about our universe. I will discuss how we can use new and complementary data sets to identify new physics at different scales.

Zoom Link: 
https://us02web.zoom.us/j/4459928099

Meeting ID: 445 992 8099

Quantum simulations can be performed at various scales: Cold atoms or trapped ions are optimal platforms when it comes to the ultimate control over the individual constituents of the simulator. Twisted bi-layer materials, on the other hand, combine the powerful tuning knobs of the traditional simulators with the direct route to applications inherent to solid state systems. Fortunately, these intermediate scale simulators present us with theoretical challenges that arise from their complexity. In this talk I will present our attempts to understand the superconductivity in twisted bi-layer graphene and how topology might play a crucial role. 

Since the beginning of the millennium, physicists know how to generate pulses of light of attosecond duration (1 as= 10-18 s), thus gaining access to this incredibly short time scale. This presentation will describe how attosecond pulses are generated when intense laser pulses interact with atomic gases, and what are their characteristics.

We will then show how these pulses can be used to investigate fast electron dynamics in atomic photoionization.

Meeting ID: 39 0317 8346

Password: 326163

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An overview is given on recent mass and g-factor measurements with extreme precision on single or few cooled ions stored in Penning traps. On the one hand, mass measurements provide crucial information for atomic, nuclear and neutrino physics as well as for testing fundamental interactions and their symmetries. On the other hand, gfactor measurements of the bound electron in highly charged hydrogen-like ions allow for the determination of fundamental constants and for constraining Quantum Electrodynamics. For example, the most stringent test of CPT symmetry in the baryonic sector could be performed by mass comparison of the antiproton with H- and the knowledge of the electron atomic mass could be improved by a factor of 13.

קישור להקלטת ההרצאה

Nano-engineered platforms for neuronal regeneration

Orit Shefi, Ph.D.

Faculty of Engineering, Institute of Nanotechnologies and Advanced Materials, Gonda Brain Center

Bar Ilan University

The ability to manipulate and direct neuronal growth has great implications in basic science and tissue engineering. Physical mechanical forces, contact guidance cues and chemical cues play key roles in neuronal morphogenesis and network formation. In this talk I will present our recent studies of 2D and 3D nanostructured scaffolds as platforms for controlling neuronal growth. We grow neurons on substrates patterned with nanotopographic cues of different shapes and materials and study the effects on neuronal geometry and function. We compare neurons interfacing the nano-patterned substrates to neurons interfacing other neurons to reveal mechanisms translating interactions into neuronal growth behavior. In-vivo, neurons grow in a 3-dimensional (3D) extracellular matrix (ECM). Imitating the 3D environment resembling the in-vivo conditions is important for effective regeneration post trauma. We have chosen a collagen hydrogel system as the 3D ECM analog to best mimic the natural environment and develop methods to orient the collagen fibers and use them as leading cues for neurons. We also used magnetic manipulations, via MNPS, as mediators to apply forces locally on neurons and their environment and as drug carriers. Current efforts to implant these modified gels to bridge gaps in injured PNS models effectively will be presented.

Meeting ID: 39 0317 8346

Password: 326163

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Materials whose individual constituents consume free energy and move autonomously as a result are known as Active Matter, for which living systems are both inspiration and prime example. I will introduce the subject, summarise early results, and present recent and ongoing work with my students and colleagues, on organising principles, phase transitions, and surprises in the statistics and dynamics of active systems. 

Zoom Meeting ID:  939 0317 8346, Password: 326163

For decades, condensed matter systems have been studied within the framework of classical order parameters - i.e. the Landau-Wilson paradigm.  This has been recently extended with the rather complete understanding of topological states of noninteracting electrons. In this talk  I will focus instead on new physics that arises from the interplay of topology and strong interactions. A unifying theme will be the emergence of gauge fields rather than the classical order parameters of Landau theory. I will illustrate these general themes with two recent works. The first  proposes a route to realizing  a long sought after phase - the Z2 quantum spin  liquid - in a synthetic platform, an array of  highly excited (Rydberg) atoms [1]. A potential application to the engineering of naturally fault tolerant quantum bits will also be described. The second example describes a topological route to strong coupling superconductivity [2], which was inspired by  recent experimental observations in magic angle  bilayer graphene and related devices.

[1] arXiv:2011.12310. Prediction of Toric Code Topological Order from Rydberg Blockade.
Authors: R. Verresen, M. Lukin and A. Vishwanath.
[2]arXiv:2004.00638. Charged Skyrmions and Topological Origin of Superconductivity in Magic Angle Graphene. 

Zoom Link: https://us02web.zoom.us/j/4459928099

Meeting ID: 445 992 8099

The observation that non-genetic variability is ubiquitous in microbial populations has led to a multitude of experimental and theoretical studies seeking to probe the causes and consequences of this variability. Whether it be in the context of antibiotic treatments or exponential growth in constant environments, variability has significant effects on population dynamics. I will first present a coarse-grained model for cell growth, inspired by the Langevin equation, which incorporates both biomass growth rate and generation time fluctuations. Building on it, we will connect single-cell variability to the population growth, showing that in contrast to the dogma growth-rate fluctuations may lower the population growth. Analogous results are derived in the case where the variability arises from the asymmetric partitioning of a cellular resource, where we find a phase transition between a regime where variability is beneficial to one where it is detrimental. We will also show that a population's growth rate can be inferred from a single lineage, with intriguing relations to large deviation theory.

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Cosmological observations and galaxy dynamics seem to imply that 84% of all matter in the universe is composed of dark matter, which is not accounted for by the Standard Model of particles. The particle nature of dark matter is one of the most intriguing puzzles of our time. The wealth of knowledge which is and will soon be available from cosmological surveys will reveal new information about our universe. I will discuss how we can use new and complementary data sets to improve our understanding of the particle nature of dark matter. In particular, galaxy-scale strong gravitational lensing provides a unique way to detect and characterize dark matter on small scales. I will present advances in the analysis of gravitational lenses and identification of small-scale clumps using machine learning. I will introduce the convergence power spectrum as a promising statistical observable that can be extracted from strongly lens images and used to distinguish between different dark matter scenarios, showing how different properties of the dark matter get imprinted at different scales. I will also discuss the different contribution of substructure and line-of-sight structure to perturbations in strong lens images.

לינק להקלטת ההרצאה: https://us02web.zoom.us/rec/share/g15AT0PA8sqcrnQMBepS6V4E0CQGAp7jukiCb…

Trapped radioactive atoms and ions have become a standard tool of the trade for precision studies of beyond SM physics. β decay studies, in particular, offer the possibility of detecting deviations from standard model predictions of the weak interaction which signal new physics. These ’precision frontier’ searches are complementary to the high energy searches performed by the LHC and other high energy/high luminosity facilities. I will present a general overview of magneto-optical, optical traps, and electrostatic traps, and their use for weak interaction studies. I will further present the new Hebrew University/Weizmann Institute/NRCN trapping program (TRAPLAB), recent experimental results, and future plans.

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Modern machine learning has had an outsized impat on many scientifc fields, and particle physics is no exception. What is special about particle physics, though, is the vast amount of theoretical and experimental knowelde that we already have about many problems in the field. In this colloquium, I present two case studies involving quantum chromodynamics (QCD), at the Large Hadron Collider (LHC) highlighting the fascinating interplay between theoretical principles and machine learning strategies. First, by catalogining the space of all possible QCD measurements, we (re)discoverd technology relevant for self-dricing cars. Second, by quantifying the similarity between two LHC collisions, we unlocked a class of nanparametric machine learining techniques based on optimal transport. In addition to providing new quantitative insights into QCD, these techniques enable new ways to visualize data from the LHC.

Recording of the talk:

https://us02web.zoom.us/rec/share/8pp1yRxYnO7IWLTkEfuWFlaHlNhri9dKfRWGv…

Zoom link: 

 https://us02web.zoom.us/j/4459928099

Meeting ID: 445 992 8099

Almost every existing method of cluster and nanoparticle formation leads to a wide distribution of sizes. Thus, the limiting factor in all cluster studies is creating a sufficiently high concentration of the desired species and separating them from the overall distribution [1]. Recently, we discovered that large helium droplets can become highly-charged [2]. The charge centers self-organize as two-dimensional Wigner crystals at the surface of the droplets and act as seeds for the growth of dopant clusters [3]. Cluster ions of a specific size and composition can be formed by this technique with unprecedented efficiency. Softlanding of metal nanoparticles formed in highly-charged helium droplets can be achieved by deposition onto a target surface. The figure below shows two transmission electron microscope images of amorphous carbon surfaces decorated with metal nanoparticles formed upon pickup into helium droplets. In the case of neutral droplets (left image, taken from [4]), a single nanoparticle is formed in every droplet and its size depends strongly on the size of the helium droplet. As a result, a wide size distribution of nanoparticles is observed and the deposition time was several hours. In contrast, pickup of gold vapor into highly-charged helium droplets (right image) results in a narrow size distribution of nanoparticles. Due to the fact that several hundred nanoparticles are formed simultaneously in one helium droplet, the deposition time was reduced to a few seconds. Several applications for cluster physics, ion spectroscopy and nanotechnology will be presented

The understanding of strongly-correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlated physics, namely moiré quantum matter. In particular, I will
show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system. These flat bands systems exhibit a plethora of quantum phases, such as correlated insulators, superconductivity, magnetism, Chern insulators, and more. Furthermore, it is possible to extend the moiré quantum matter paradigm to systems beyond magic angle graphene, and I will present an outlook of some exciting directions in this emerging field.

Link to zoom: https://weizmann.zoom.us/j/93903178346

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The lecture will take place via Zoom: https://us02web.zoom.us/j/4459928099  Meeting ID: 445 992 8099

Gravitational Waves were originally predicted in the 1910's by Einstein, and measured directly for the first time in 2015. In the 5 years since, they have become a household acquaintance and a cornerstone of astrophysical observations and discoveries. I will present their background, history, and how they have begun to shape current day astrophysics, as well as what is expected in the not-so-distant future.

Link to the recording of the lecture

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2D systems have been in the focus of condensed matter physics for decades. Recently it was shown that a twist between a pair of 2D graphene sheets at a particular ‘magic angle’  transfers the bilayer system to the strongly interacting regime. In this talk I will explain the ‘magic angle’ theory and review recent experimental results that demonstrate why twisted 2D  systems provide an excellent playground for studying some of the most fundamental open questions in condensed matter physics.

The colloquium will take place via Zoom and can be accessed through the followin link:

https://zoom.us/j/4459928099

Meeting ID: 445 992 8099

Note: The colloquium will take place via ZOOM:  https://zoom.us/j/4459928099

Meeting ID: 445 992 8099
 

Electromagnetic fields possess zero point fluctuations which lead to observable effects such as the Lamb shift and the Casimir effect. In the traditional quantum optics domain, these corrections remain perturbative due to the smallness of the fine structure constant. To provide a direct observation of non-perturbative effects driven by zero point fluctuations in an open quantum system we wire a highly non-linear Josephson junction to a high impedance transmission line, allowing large phase fluctuations across the junction [1]. Consequently, the resonance of the former acquires a relative frequency shift that is orders of magnitude larger than for natural atoms. Detailed modeling confirms that this renormalization is non-linear and quantum. Remarkably, the junction transfers its non-linearity to about thirty environmental modes, a striking back-action effect that transcends the standard Caldeira-Leggett paradigm. This work opens many exciting prospects for longstanding quests such as the tailoring of many-body Hamiltonians in the strongly non-linear regime, the observation of Bloch oscillations,or the development of high-impedance qubits.

[1] Léger, S., Puertas-Martínez, J., Bharadwaj, K. et al. Observation of quantum many-body effects due to zero point fluctuations in superconducting circuits. Nat Commun 10, 5259 (2019)

Note: The colloquium will take place thorough zoom via the link: https://zoom.us/j/4459928099

Meeting ID: 445 992 8099

There are many occurrences of fluorescence and bioluminescence in nature, e.g., the Green Fluorescent Protein (GFP) or the luciferase enzyme that is responsible for light emission from fireflies. The photoactive molecules within these two proteins are both negatively charged (anions) and are surprisingly non-fluorescent when isolated in vacuo. Which interactions with the protein microenvironment are needed to turn on the fluorescence? This question is not only interesting from a fundamental point of view but also in biotechnology. Indeed, much work is devoted to develop bright fluorescent proteins or dyes in the red region of the visible spectrum where tissue transmission is high. My group tackles the question from a bottom-up approach as we study isolated molecular ions in vacuo and their intrinsic photophysics. In addition to protein biochromophores, we are interested in ionic dyes that are used in Förster Resonance Energy Transfer (FRET) experiments. Our work is based on home-built instruments, one important one being LUNA (LUminescence iNstrument in Aarhus) that allows us to measure fluorescence from larger ions produced by electrospray ionization. We have used this setup to study rhodamine monomer cations as well as homodimers (two identical dyes) and heterodimers (two different dyes) where the two dye cations are separated by flexible methylene linkers or more rigid linear linkers. In the case of heterodimers we see clear evidence of FRET in gas-phase systems, i.e., energy transfer from the initially photoexcited donor dye to the acceptor dye. I will present the results and discuss how the presence of one dye significantly affects the other. One of our future goals is to turn on light emission from protein biochromophores, either by cooling to low temperatures or by the attachment of polar molecules. This may be accomplished with a new setup (LUNA2) where the luminescence cell (trap) is cooled to liquid nitrogen temperature.

The Cryogenic Storage Ring (CSR) at the Max Planck Institute for Nuclear Physics in Heidelberg combines electrostatic ion optics with extreme vacuum and cryogenic temperatures [1]. The storage ring has a circumference of ~35 m, and the detectors are housed in experimental vacuum chambers that can be cooled down to 5K. It has been shown that within a few minutes of storage infrared-active molecular ions (e.g., CH+ [2] and OH-[3]) cool to their lowest rotational quantum states by spontaneous emission of radiation.

Equipped with an ion-neutral collision setup and a low-energy electron cooler, the CSR offers unique possibilities for astrochemical experiments under true interstellar conditions. We will present an overview of the capabilities of the CSR along with first experimental
results on collisions of neutral C atoms with various hydrogen molecular ions and on the electron recombination of HeH+ [4].

Please note: The colloquium will take place via zoom. Join the meeting via the link:  https://zoom.us/j/4459928099

Meeting ID: Meeting ID: 445 992 8099

References
[1] R. von Hahn, et al., The Cryogenic Storage Ring CSR, Rev. Sci. Instrum. 87, 063115 (2016)

[2] A. O'Connor, et al., Photodissociation of an Internally Cold Beam of CH+ Ions in a Cryogenic Storage Ring, Phys. Rev. Lett 116, 113002 (2016)

[3] Ch. Meyer, et al., Radiative Rotational Lifetimes and State-Resolved Relative Detachment Cross Sections from Photodetachment Thermometry of Molecular Anions in a Cryogenic Storage Ring, Phys. Rev. Lett. 119, 02320 (2017)

[4] O. Novotny, Quantum-state-selective electron recombination studies suggest enhanced abundance of primordial HeH+, Science 365, 676 (2019)

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A major achievement in the study of complex networks is the observation that diverse systems, from sub-cellular biology to social networks, exhibit universal topological characteristics, such as the small world or the scale-free phenomena. Yet this universality does not naturally translate to the dynamics of these systems, hindering our progress towards a theoretical framework of network dynamics. The source of this theoretical gap is the fact that the behavior of a complex system cannot be uniquely predicted from its topology, but rather depends also on the dynamic mechanisms of interaction between the nodes, hence systems with similar structure may exhibit profoundly different dynamic behavior. To bridge this gap, we derive the patterns of network information flow, indeed, the essence of a network's behavior, by offering systematic translations of topological characteristics into the actual spatiotemporal propagation of perturbative signals.

Relevant papers:

• Spatiotemporal propagation of signals in complex networks. Nature Physics 15, 403 (2019)
• Patterns of information flow in complex networks. Nature Communications 8, 2181 (2017)
• Universal resilience patterns in complex networks. Nature 530, 307 (2016)
• Universality in network dynamics. Nature Physics 9, 673 (2013)

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‘Neural network (NN)’ is one of the new buzz words, but ‘neuromorphic’ is barely known outside of geeky community. It means ‘to mimic biological architectures in the nervous system’. As is well-known, the nervous system is in extreme complexity; mimicking the whole architecture is impossible. Thus, the essential point is abstraction.The biological neuron, an electrically excitable cell that communicates with
each other, can be replaced by a nonlinear device (artificial neuron) with a threshold for logic functions. The biological synapse, a joint between two neurons, with neuroplasticity can be a memory device (artificial synapse). The artificial neurons and synapses lead to the formation of artificial NN (ANN), and the architecture of ANN is crucial. Ideally, the properties of the artificial neuron and synapse should
determine the architecture of ANN. If the artificial neuron can mimic ‘leaky-integrate and fire (LIF)’ property, and the artificial synapse can mimic ‘spike-time-dependent plasticity (STDP)’ property of the biological counterparts, a spiking neural network (SNN) is plausible. However, in the present research, algorithm plays the leading role to determine both the architecture and devices, though the biological nervous system does not have any algorithms at all. An interesting example is the deep-learning (DL) algorithm for multi-layer NN. Because of its remarkable success in highly efficient statistical processing (e.g., image recognition), development of DL algorithm and computer chip for multi-layer NN (i.e., DL accelerator) are believed to realise artificial intelligence. However, the brain does not work with any algorithms. Our brain consumes only 20W, while DL requires immense power (Alpha Go, which defeated world champion, needed 200 kW), because the algorithm requires huge logic calculations.
In this talk, I would like to give an introduction of the abstraction for preparing the neuromorphic devices and architectures. I would also like to discuss on how to escape from the kingdom of the DL algorithm for real brain-like low-power computation.

Short Biography
Dr Isao H. Inoue received BSc, MSc, and DSc degrees in Physics from the University of Tokyo in 1990, 1992 and 1999, respectively. He became a researcher with tenure at the Electrotechnical Laboratory (ETL) in 1992 and a senior researcher in 1999. From 1999 to
2001, Dr Inoue was a visiting scholar at Cavendish Laboratory, University of Cambridge. In 2001, the Japanese government reorganised ETL with several other national institutes to found the National Institute of Advanced Industrial Science and Technology (AIST). Since then, he has been a senior researcher of AIST trying to work on missing links between the fundamental physics and the emerging electronics: e.g., quantum critical phenomena and neuromorphic electronic devices.

isaocaius@gmail.com; https://sites.google.com/view/isao/

We are in the midst of a revolution in genome engineering and CRISPR-Cas9 technology was the spark. With unprecedented rapidity, this technology has provided a straightforward, robust, and specific method for genome engineering and gene correction. CRISPR-Cas9 is a technique that allows for highly rapid modification of DNA in genomes of organisms and/or of cells. Our research focuses on developing CRISPR genome engineering as curative therapy for genetic diseases. Our lab is particularly interested in applying genome engineering for gene therapy of genetic disorders of the blood and the immune system such as severe combined immunodeficiency (SCID) also commonly known as the “bubble boy” disease. SCIDs are a set of life threatening genetic diseases in which patients are born with mutations in single genes, and are unable to develop functional immune system. We believe that the ultimate cure for these diseases will be transplantation of gene-corrected stem cells that create normal and healthy immune system. To be able to apply this approach in the clinic, we must assure that the CRISPR genome engineering technology is efficient and safe. Hence, our research focuses on developing an optimized CRISPR genome engineering for robust, specific and non-toxic gene correction. In my talk I will present the concept of CRISPR genome engineering and its possible application in medicine. I will present some of our recent studies demonstrating enhanced CRISPR genome editing by using chemical alterations to the CRISPR system, enabling therapeutically relevant genome editing frequencies in stem cells of the blood and the immune system. Finally, I will also present our joint research with the Yakhini group on developing an approach to accurately measure CRISPR specificity. Overall, we believe that by advancing CRISPR technology our research will accelerate the bench to bedside path and will help in generating a clear trajectory towards future clinical trials.

Morphogenesis, the emergence of functional form in a developing organism, is one of the most remarkable examples of pattern formation in nature. Despite substantial progress, we still do not understand the organizational principles underlying the convergence of this process, across scales, to form viable organisms under variable conditions. We focus on the mechanical aspects of morphogenesis using Hydra, a small multicellular fresh-water animal, as a model system. Hydra has a simple body plan and is famous for its ability to regenerate an entire animal from small tissue pieces, providing a flexible platform to explore how mechanical forces and feedback contribute to the formation and stabilization of the body plan during morphogenesis. I will present our recent results showing that the nematic order of the supra-cellular actin fibers in regenerating Hydra defines a coarse-grained field, whose dynamics provide an effective description of the morphogenesis process. In particular, I will show that topological defects in the nematic order of the actin fibers act as organization centers of the morphogenesis process, with the main morphological features developing at defect sites. Finally, we aim to directly demonstrate that mechanical constraints can pattern the body plan during morphogenesis via mechanical feedback and I will describe our progress in this direction.

In solid materials where electrons are strongly interacting, their spin and charge may effectively split to separate degrees of freedom. An extreme manifestation of this phenomena is the complete freezing of the charge degree of freedom (which renders the material electric insulator) while charge-neutral spin excitations are potentially free to move. When such materials possess a crystalline structure that frustrates magnetic ordering, novel phases of matter can form at low temperatures due to the quantum nature of the spin degrees of freedom. Among the most exotic states of matter emerging in these systems are the so-called "spin liquid" phases. Under appropriate conditions, they possess an intriguing signature: a thermal Hall effect in the absence of electric current. I will describe a particular model for spin-1/2 particles on a frustrated lattice which supports such quantum phases, and the behavior of the resulting thermal Hall conductance in the presence of an external magnetic field. Most prominently, we find that tuning the magnetic field induces transitions among three distinct phases: a spin-insulating valence bond crystal, a metallic spin-liquid and a chiral spin-liquid; the latter is an analogue of a quantum Hall liquid in two-dimensional conductors. I will finally discuss the possible relation of these findings to experimental observations of the recent years.              

Measurements in quantum physics, unlike their classical physics counterparts, can fundamentally yield discrete and random results. Historically, Niels Bohr was the first to hypothesize that quantum jumps occurred between two discrete energy levels of an atom. Experimentally, quantum jumps were directly observed many decades later in an atomic ion driven by a weak deterministic force under strong continuous energy measurement. The times at which the discontinuous jump transitions occur are reputed to be fundamentally unpredictable. Despite the non-deterministic character of quantum physics, is it possible to know if a quantum jump is about to occur? Our work¹ provides a positive answer to this question: we experimentally show that the jump from the ground state to an excited state of a superconducting artificial three-level atom can be tracked as it follows a predictable “flight” by monitoring the population of an auxiliary energy level coupled to the ground state. The experimental results demonstrate that the evolution of the jump — once completed — is continuous, coherent, and deterministic. Based on these insights and aided by real-time monitoring and feedback, we then pinpoint and reverse one such quantum jump “mid-flight”, thus deterministically preventing its completion. Our findings, which agree with theoretical predictions essentially without adjustable parameters, lend support to the modern formulation of quantum trajectory theory; most importantly, they may provide new ground for the exploration of real-time intervention techniques in the control of quantum systems, such as the early detection of error syndromes.

1. Z. Minev et al., Nature 570, 200–204 (2019)

Can one construct a thinking machine?  Is artificial intelligence on the road to producing a thinking machine?  As computer programs become more and more sophisticated, will computers eventually be able to think?  How far away are we from such a possibility?  What does one mean by “thinking”?  Will thinking computers be able to decide to injure people?  To enslave mankind or maybe even to destroy mankind?  What is the Chinese Room thought experiment proposed by John Searle?  What are the implications of this thought experiment?  What reactions has this thought experiment generated?

These are some of the questions that will be discussed in this talk.

The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field ground-based telescope designed to provide a time-domain imaging survey of the entire southern hemisphere of sky in six optical colors (ugrizy).  Over ten years, LSST will obtain ~ 1,000 exposures of every part of the southern sky, enabling a wide-variety of distinct scientific investigations, ranging from studies of small moving bodies in the solar system, to constraints on the structure and evolution of the Universe as a whole.

The development of LSST is a collaboration between the US National Science Foundation, which is supporting the development of the telescope and data system, and the US Department of Energy, which is supporting the development of the 3.2 gigapixel camera, the largest digital camera ever fabricated for astronomy.  Approved in 2014, LSST is now well into construction, and is on track to beginning operations in 2022.  I will review the design and technical status of the Project, and provide an overview of some of the exciting science highlights that we expect to come from this facility.

Quantum phenomenon in curved spacetimes is an intriguing research topic that aims to offer hints to the not-yet-known theory of quantum gravity. One famous prediction is the Hawking-Unruh effect, the manifestation of Minkowski vacuum in a reference frame with high acceleration. We simulate the transformation to an accelerating frame by parametrically driving a Bose-Einstein condensate of atoms. Above the critical threshold, the driven condensate suddenly emits many jets of matterwaves in all directions. The emission resembles fireworks and displays a Boltzmann distribution that resembles the Unruh radiation. The measured temperature and entropy are in excellent agreement with Unruh’s predictions. We further detect non-local quantum coherence and temporal reversibility of the matterwave emission, which are hallmarks that distinguish Unruh radiations from the classical blackbody radiation. Our results confirm the quantum nature of Unruh effect.

Remarkable breakthroughs in science throughout history are inherently linked to advances in the study of light-matter interactions. The understanding of new physical concepts and the development of novel optical tools were the driving forces behind ground-breaking multi-disciplinary discoveries in a variety of research fields. For the past two decades we have witnessed major advances in nano-optics and ultrafast physics, allowing for the exploration of phenomena in higher spatial and temporal resolution than ever before. In my talk, I will present recent achievements of observation and control of ultrafast phenomena at the nanoscale. In particular, I will share our recent achievements in combining ultrabroadband sources with our scattering near field microscope allowing observation of the broad frequency response as well as the ultrafast transient dynamics of plasmonic systems. I will share experimental demonstration of coherent control of the nonlinear response of optical second harmonic generation in resonant nanostructures beyond the weak-field regime. Contrary to common perception, we show that maximizing the intensity of the pulse does not yield the strongest nonlinear exponential response. We show that this effect emerges from the temporally asymmetric photo-induced response in a resonant mediated non-instantaneous interaction, opening new and diverse applications for control of optical nonlinearities at the nanoscale.

Active Galactic Nuclei (AGN) can produce steady state luminosity which far exceeds the luminosity of a whole galaxy. Observations indicate dilute gas which is present close to the massive black hole which resides at the centre of AGN. The energy transmitted from the radiation to the gas is well studied, but the momentum transfer did not receive much attention. I will describe the universal structure induced by the incident radiation pressure, and how it can naturally explain a host of emission and absorption properties of the ambient gas. Possible relevance to other systems will be briefly mentioned.

Supernovae distribute most of the chemical elements that we are made of and are detected daily, yet we still do not know how they explode. Type Ia supernovae consist of most recorded supernovae and are likely the result of thermonuclear explosions of white dwarfs (common compact stars with mass similar to the sun and radius similar to earth), but what mechanism causes about 1% of white dwarfs to ignite remains unknown. I will describe our ongoing recent attempt to solve this puzzle that involves a new potential answer - direct collisions of white dwarfs in multiple stellar systems, new robust tools to compare explosion models to observations - in particular the use of global conservation of energy in emitted radiation,  and new key observations  - in particular late-time spectra of ~100 recent supernovae.

The electron’s spin is essential to the structure of matter and control over the spin orientation opens avenues for manipulating the structure of molecules and materials.  The energy associated with interacting electron clouds changes with their relative spin orientation. Controlling the relative spin orientation of electrons located on two reactants (atoms, molecules, or surfaces) has proved challenging, however. Recent developments based on the Chiral Induced Spin Selectivity (CISS) effect show that the spin orientation is linked to molecular symmetry and can be controlled in ways not previously imagined. For example, the combination of chiral molecules and electron spin opens a new approach to (enantio)selective chemistry, by adsorbing chiral molecules on a superconducting surface the order parameter is changes.  In my talk I will review the theoretical concepts underlying the CISS effect and illustrates its importance by discussing some of its manifestations in Chemistry, Biology, Physics and Spin based device engineering.

Copper's ability to accept and donate single electrons makes it an ideal redox cofactor, and thus one of the most essential metal ions to the survival of the cell. However, copper ions are also involved in the Fenton reaction and hence capable of driving the generation of hydroxyl radicals, which are deleterious to the cell. Hence, both prokaryotic systems as well as eukaryotic system have developed a considerable regulation mechanism to maintain negligible copper concentration, in the femtomolar concentration. E.coli cells, in common with the vast majority of bacterial cells, require copper for several important enzymes such as ubiquinole oxidases, Cu,Zn-superoxide dismutases, or cytochrome c oxidase. However, as was mentioned above, copper can be deleterious, making protective mechanisms necessary. Deciphering this regulation mechanism in bacteria, is tremendously important from two specific reasons: one over 70% of the putative cuproproteins identified in prokaryotes have homologs in eukaryotes, and thus resolving the copper cycle in prokaryotic systems will also shed light on the copper cycle in eukaryotic systems. Second, copper has been used throughout much of the human civilization as an antimicrobial agent. In this talk we will shed light on two important copper regulation systems in E.coli: the copper periplasmic efflux system, CusCFBA, and the Cu(I) metal sensor, gene expression regulation system, CueR. Using Electron Paramagnetic Resonance (EPR) spectroscopy, together with biochemical experiments, cell experiments, and computational methods we will present structural model for CusB and CueR in the apo and functional state. Then, based on the structural constraints and cell data we will explain their mechanism of action. Last, we will demonstrate how basic understanding of the function of these systems can assist us in designing new class of antibiotics.

Active Galactic Nuclei (AGN) can produce steady state luminosity which far exceeds the luminosity ofa whole galaxy. Observations indicate dilute gas which is present close to the massive black hole which resides at the centre of AGN. The energy transmitted from the radiation to the gas is well studied, but the momentum transfer did not receive much attention. I will describe the universal structure induced by the incident radiation pressure, and how it can naturally explain a host of emission and absorption properties of the ambient gas. Possible relevance to other systems will be briefly mentioned.

Single spin detection is one of the central challenges of nano science and technology. We have
developed an STM related technique for single spin magnetic resonance (ESR-STM). The importance
of such a technique is three-fold: chemical analysis on the nm or atomic scale; Single spin physics
(many of the new physical phenomena recently observed are spin related: High temperature
superconductivity; Dirac materials; topological insulators etc and quantum information and
computation using single spin qubits.)
We measure high frequency noise power densities in the STM tunneling current. When above a
single spin in an external magnetic field, it reveals peaks at the Larmor frequencies. This is done at
room temperature, and without spin polarized tunneling. In order to detect weak rf signals (of the order
of 1-3 pA) we use matching circuits, modulation techniques and sensitive detectors (spectrum
analyzers or rapid oscilloscopes).
ESR-STM measurements on different spin centers revealed g hyperfine and zero field splitting
tensors up to a single spin levels. This reveals information on the local environment of the single spin
– which is not detectable microscopically. We use the hyperfine levels for doing single spin double
resonance measurements to detect the nuclear transitions. The experiments are performed on magnetic
atoms, defects or molecules. Studies to extend the technique for non magnetic species by ionization are
in progress.
Current results have demonstrated the capability to detect a single spin hyperfine spectrum of one
Tempo molecule. When there is another molecule nearby, the dipolar interaction between the
molecules, modifies the spectrum and enables to calculate the distance between the two molecules.
The distance is in agreement with the STM image. This ability may have broad applications for
example in questions of molecular docking or in molecular magnets

RNA editing is a post-transcriptional process that allows for diversification of proteomes beyond the genomic blueprint, a phenomenon called "recoding". However, it is infrequently used among animals for this purpose. I will review the state-of-the-art understanding of recoding by editing, and discuss at length recent results showing that recoding is particularly common in behaviorally sophisticated coleoid cephalopods (e.g. squid and octopus). In particular, the trade-off between genome evolution and transcriptome plasticity will be suggested as a partial explanation for the rarity of recoding in most animal species.

Nuclear and radiation hazards, historically linked to nuclear apocalypse, have been considerably overestimated. In the presentation, short consideration of nuclear detonations and their consequences (serious but far not apocalyptic) is followed by comparison to an interesting related phenomenon: nuclear-weapon-sized detonations of meteoroids in the atmosphere. Then, we proceed to considering radiation risks. The linear no-threshold (LNT) model, based on the assumption that every radiation dose increment constitutes increased cancer risk for humans, arose in late 1950-s concurrently with the nuclear arms race and massive governmental investment in science. Mistreatment of experimental (epidemiological) data systematically lent support to LNT. The presentation will describe our meta-analysis of several studies including Japanese atomic bomb survivors, Chernobyl and Fukushima residents, and children subjected to CT scans. The results of the meta-analysis show that (1) the Japanese data lack statistical power to support LNT, (2) recently-acknowledged overdiagnosis of thyroid cancer (reaching 90% and more of the reported incidence) is the main factor of increase in cancer incidence after Chernobyl and Fukushima, and (3) the data fit demonstrating increased risk of cancer after CT scans in childhood is "too good to be honest", so the data have been probably manipulated somehow. In addition, our recent analysis showed that even assuming LNT true, the present guidelines for population evacuation in case of radiological emergency are at least five-fold too stringent; the overall effect of such evacuations (including those after Chernobyl and Fukushima) is life shortening instead of the intended life extension.

Controlling the optical field down to the nanometer scale is a key step in optoelectronic applications and light–matter interaction at the nanoscale. Bowtie structures, rods, and sharp tapers are commonly used to realize such optical properties, but their fabrication is challenging. In this context, the complementary structures, namely, holes and cavities, are less explored. Herein, a simple system of two metallic nanocavities milled in thin silver film is used to confine the electromagnetic field to an area of ≈60 nm2. The field is confined onto a flat surface area and is either enhanced or suppressed by the polarization state of incident light. The energy of this spatially confined mode is determined by the distance between the two cavities and thus any color (wavelength) at the optical regime can be achieved. As a consequence, a dynamically controlled color is generated on an optical pixel size smaller than 1 μm2. We further characterize those surfaces by a set of complementary spectroscopic technique among them; linear optical imaging, cathodoluminescence and second harmonic generation (SHG). A different mechanism for generating SHG is discussed, suggesting that the plasmons propagating onto the surface act as elementary particles and annihilate to form locally SHG spot.

(1) Galanty, M., Shavit, O., Aharon, H. Gachet, D. & Salomon, A.* Second Harmonic Generation Hot-Spot on a Centrosymmetric Smooth Silver Surface. light: Science and application

(2) Weissman, A.; Galanty, M.; Gachet, D.; Segal, E.; Shavit, O.; Salomon, A. Spatial Confinement of Light onto a Flat Metallic Surface Using Hybridization between Two Cavities. Adv. Opt. Mater. 2017,

(3) Segal, E.; Weissman, A.; Gachet, D.; Salomon, A. Hybridization between Nanocavities for a Polarimetric Color Sorter at the Sub-Micron Scale. Nanoscale 2016. (4) Grosse, N. B.; Heckmann, J.; Woggon, U. Physical Review Letters 2012, 108 (13), 136802.

Novel wide-field transient surveys of the sky are finding new types of astronomical phenomena. I will discuss three classes of events we discovered recently: (1) peculiar new types of stellar explosions, which are challenging well-established models of supernova power sources; (2) the disruptions of stars by supermassive black holes, which are providing new insights into a decades-long problem; and (3) neutron stars mergers, which have brought the first observations of an astronomical event in both gravitational and electromagnetic waves, providing new insights (but also new puzzles) from the nuclear scale to the Universe as a whole. As more surveys come online in the coming years, we must develop the ability to define and identify the interesting events and obtain the crucial data in real time. I will briefly discuss how we're addressing this challenge.

Backward Raman amplifiers provide a promising path to the next generation of short pulse high-intensity lasers that can go beyond the damage limit of conventional materials [1]. The main idea is to couple a short seed and a long counter-propagating pump through an electron plasma wave in such a way that the pump energy is transferred to the seed that is amplified and compressed via Raman backscattering. In the talk, I will give a short introduction on the physics of Raman amplifiers and review three recent developments in the field: (a) mitigating the relativistic phase-mismatch and the resulting saturation by detuning of the pump pulse [2], (b) multi-frequency amplification of pulses with a beat-wave waveform [3], and (c) a new configuration for Raman amplifiers in which, the laser seed is replaced by a plasma wave seed [4].

[1] V. M. Malkin, G. Shvets, and N. J. Fisch, Phys. Rev. Lett. 82, 4448 (1999).

[2] I. Barth, Z. Toroker, A. A. Balakin, and N. J. Fisch, Phys. Rev. E 93, 063210 (2016).

[3] I. Barth and N. J. Fisch, Phys. Rev. E 97, 033201 (2018).

[4] K. Qu, I. Barth, and N. J. Fisch, Phys. Rev. Lett. 118, 164801 (2017). 

I will present current thoughts on the place of humans (on Earth) in the grand cosmical scheme, in light of astronomical observations in the last few decades.

I will also discuss some philosophical implications of these findings.

In this talk, I present an review of recent results [1,2,3] for the elastic properties of 2D crystalline membranes, including graphene. I discuss how an interplay between quantum and classical anharmonicity-controlled fluctuations leads to unusual elastic properties of the crystalline membrane. In particular, I discuss how anomalous Hooke’s law leads to the negative and almost constant thermal expansion coefficient in a wide temperature range and how the third law of the thermodynamics is restored at extremely low temperatures. Also, I discuss why the anomalous Hooke’s law is responsible for negative absolute and differential Poisson ratios of the crystalline membrane. I present the overall dependence of the Poisson ratio on the stress and the membrane size. I explain a possible reason of discrepancy in the results for the Poisson ratio between the self-consistent screening theory of membrane and numerical simulations.


[1] I.S. Burmistrov, I.V. Gornyi, V.Yu. Kachorovskii, M.I. Katsnelson, A.D. Mirlin, Phys. Rev. B 94, 195430 (2016).
[2] I.S. Burmistrov, I.V. Gornyi, V.Yu. Kachorovskii, M.I. Katsnelson, J.H. Los, A.D. Mirlin, Phys. Rev. B 97, 125402 (2018).

[3] I.S. Burmistrov, I.V. Gornyi, V.Yu. Kachorovskii, A.D. Mirlin, Annals of Physics 396, 119 (2018).

Random scattering of light in complex samples such as biological tissue renders most objects opaque to optical imaging techniques, diffusing every focused beam into a complicated speckle pattern. However, although random, scattering is a deterministic process, and it can be undone and also exploited by controlling the incident optical wavefront, using computer controlled spatial light modulators (SLMs). These insights form the basis for the emerging field of optical wavefront-shaping [1]. Opening the path to new possibilities, such as imaging through visually opaque samples and around corners [2].

The major challenge in the field today is in determining the required wavefront correction without accessing the far side (target side) of the scattering sample.

I will present some of our recent efforts in addressing this challenge [3-8]. These include the use of optical nonlinearities [3], the photoacoustic effect [4-6], and acousto-optics [7] to focus and control light non-invasively inside scattering samples. I will also show how by exploiting inherent correlations of scattered light, it is possible to image through scattering layers and ‘around corners’ using nothing but a smartphone camera [8].

If time permits, I will present the use of these principles for endoscopic imaging through optical fibers [9-10].

References

[1] A.P. Mosk et al., "Controlling waves in space and time for imaging and focusing in complex media", Nature Photonics 6, 283 (2012).

[2] O. Katz et al., "Looking around corners and through thin turbid layers in real time with scattered incoherent light", Nature Photonics 6, 549 (2012).

[3] O.Katz et al., "Noninvasive nonlinear focusing and imaging through strongly scattering turbid layers", Optica, 1, 3, 170-174 (2014).

[4] T. Chaigne et al. "Controlling light in scattering media noninvasively using the photo-acoustic transmission-matrix.", Nature Photonics 8, 58 (2014).

[5] E.Hojman et al. "Photoacoustic imaging beyond the acoustic diffraction-limit with dynamic speckle illumination and sparse joint support recovery", Optics Express Vol. 25, Issue 5, pp. 4875-4886 (2017)

[6] T. Chaigne et al. "Super-resolution photoacoustic imaging via flow-induced absorption fluctuations", Optica Vol. 4, Issue 11, pp. 1397-1404 (2017)

[7] O. Katz et al. " Controlling light in complex media beyond the acoustic diffraction-limit using the acousto-optic transmission matrix", Nature Communications (2019)

[8] O. Katz et al., "Non-invasive single-shot imaging through scattering layers and around corners via speckle correlations", Nature Photonics, 8, 784–790 (2014)

[9] A.Porat et al., "Widefield lensless imaging through a fiber bundle via speckle-correlations", Optics Express (2016)

[10] SM Kolenderska, O Katz, M Fink, S Gigan Scanning-free imaging through a single fiber by random spatio-spectral encoding, Optics letters 40 (4), 534-537 (2015)

According to standard theory, systems with a low concentration of charge carriers, such as semiconductors and semimetals, are not expected to exhibit superconductivity. Their density of states is very small and their Fermi energy is of the same order as the Debye frequency of the crystal. Nonetheless, superconductivity is observed in many low-density systems. In this talk I will give an overview of the theoretical challenges in understanding this phenomena and discuss possible resolutions. I will then focus on a particular scenario, a crystal close to a ferroelectric quantum critical point, in which our theory predicts superconductivity at arbitrary low density.  

Phase transitions of mixed nature, which on the one hand exhibit a diverging correlation length as in second order transitions and on the other hand display a discontinuous order parameter as in first order transitions have been observed in a diverse classes of physical systems. Examples include DNA denaturation, models of wetting, glass and jamming transitions, rewiring networks  and some one-dimensional models with long-range interactions. An exactly soluble Ising model which provides a link between some of these rather distinct classes of systems is introduced. Renormalization group analysis which provides a common framework for studying some of these systems, elucidating the relation between them will be discussed as well as the extreme value statistics of the locally ordered domains that characterize the various phases.

An arrangement of particles is said to be "hyperuniform" if its density fluctuations over large distances are strongly suppressed relative to a random configuration. Crystals, for example, are hyperuniform. Recently, several disordered materials have been found to be hyperuniform. Examples are sheared suspensions and emulsions, and, possibly, random close packings of particles. We show that externally driven particles in a liquid suspension (as in sedimentation, for example) self-organize hyperuniformly in certain directions relative to the external force. This dynamic hyperuniformity arises from the long-range coupling, induced by the force and carried by the fluid, between the concentration of particles and their velocity field. We obtain the general requirements, which the coupling should satisfy in order for this phenomenon to occur. Under other conditions (e.g., for certain particle shapes), the coupling can lead to the opposite effect -- enhancement of density fluctuations and instability. We confirm these analytical results in a simple two-dimensional simulation.

We consider quantum dynamics on a graph, with repeated strong measurements performed locally at a fixed time interval τ. For example a particle starting on node x and measurements performed on another node x'. From the basic postulates of quantum mechanics the string of measurements yields a sequence no,no,no, ... and finally in the n-th attempt a yes, i.e. the particle is detected. Statistics of the first detection time nτ are investigated, and compared with the corresponding classical first passage problem. Dark states, Zeno physics, a quantum renewal equation, winding number for the first return problem (work of A. Grunbaum et al.), total detection probability, detection time operators and time wave functions are discussed.

References

[1] H. Friedman, D. Kessler, and E. Barkai, Quantum walks: the first detected passage time problem, Phys. Rev. E. 95, 032141 (2017). Editor's suggestion.

[2] F. Thiel, E. Barkai, and D. A. Kessler, First detected arrival of a quantum walker on an infinite line, Phys. Rev. Lett. 120, 040502 (2018).

Earthquakes often trigger soil liquefaction: Usually saturated soils behave like elastic solids, supporting buildings and structures. But shaking induced by an earthquake may cause soils to undergo a rheological transition whereby they start flowing like fluids. Earthquake-triggered liquefaction causes sinking and tilting of buildings, floatation of buried structures (e.g. gas pipes), and ground settlement. This is one of the largest hazards from earthquakes: For example, liquefaction triggered during the 1995 Kobe earthquake in Japan caused 5000 deaths and $ 200 billion in damage.

The classical mechanism for explaining earthquake-triggered liquefaction invokes a poorly drained, loosely packed, saturated soil (i.e. granular media) undergoing cyclic shear. The cyclic-shearing causes pore collapse. The pressure of fluid trapped in the pores (pore pressure) then rises till the fluid fully carries the weight of the grains, permitting complete loss of shear resistance. This view is what guides current engineering practices and building codes.

Field observations from around the world show however that this only part of the story: in contrast to this widely held view, liquefied soils may be fully drained, and initially densely packed. We develop a physics based theory for treating granular and fluid deformation, and use it simulate liquefaction in a coupled multi scale discrete element + fluid code. Our theory predicts the conditions for pore collapse and explores the conditions when subsurface fluid flow can cause liquefaction. It also explains why buildings sink during liquefaction, pipes float, how remote earthquakes can trigger liquefaction, and why liquefaction can occur some time after the earthquake has passed. These results may greatly impact hazard assessment and mitigation in seismically active areas.

The colloquium is cancelled.

Today’s electronic technology – the pixels on the screen and the process to print the words on the page – are all made possible by the controlled motion of an electron’s charge. In the last decade, the discovery of topological band insulators with robust spin-polarized surface states has launched a new subfield of physics promising a new paradigm in computing. When topology is combined with strong electron correlations, even more interesting states of matter can arise, suggesting additional applications in quantum computing. Here we present the first direct proof of a strongly correlated topological insulator. Using scanning tunneling microscopy to probe the real and momentum space structure of SmB6, we quantify the opening of a Kondo insulating gap. Within that gap, we discover linearly dispersing surface states with the heaviest observed Dirac states in any material – hundreds of times the mass of a free electron. We show how single atom defects can scatter these surface states, which paves the way towards manipulating single atoms and thus controlling surface states and their excitations at the nanoscale.

Real-space (left) and momentum-space (right) images of the topological surface states on SmB6.

In the semiclassical picture of thermal and thermoelectric transport, heat-carrying quasi-particles such as electrons and phonons are scattered after traveling a finite distance. The two signatures of this picture are the Wiedemann-Franz law and Mott’s formula. The first part of this talk reviews our present picture of transverse thermoelectricity (Nernst) and transverse thermal (Righi-Leduc or thermal Hall) effects, with a focus on the extreme variety of the magnitude of the Nernst coefficient in metals explained by the semiclassical picture.

The second part of the talk is devoted to non-trivial electronic topology. The thermoelectric and thermal counterparts of the anomalous Hall effect arise because of the Berry curvature of electrons when the host solid lacks time-reversal symmetry. Our ongoing research aims to measure and to understand the transverse thermoelectric and thermal responses caused by the ‘anomalous velocity’ of electrons in magnetically-ordered solids.

Warm atomic vapor is one of the simplest quantum systems, offering real-life applications in deployable centimeter-size devices. It strongly couples to optical fields and exhibits superb coherence properties at or above room temperature. Notably, atomic vapors are at the heart of miniature atomic clocks and inside the most sensitive magnetometers and gyroscopes. We explore schemes for realizing optical quantum memories in alkali vapors and noble-gases. We realize a fast ladder-type memory (FLAME) by mapping the optical field onto the superposition between electronic orbitals in rubidium. FLAME demonstrates GHz-bandwidth and extremely low noise, suitable for quantum network synchronization. We consider the implementation of FLAME via tapered fibers, and its integration with Rydberg-level excitations for quantum nonlinear optics. On the other side of the scale, we report on a record memory lifetime approaching one second at room temperature. The long lifetime is achieved by mapping the optical field onto ground-state spin orientation of cesium, which is insensitive to spin-exchange collisions. The scheme paves the way towards relying on spin exchange for coupling light coherently to noble-gas nuclear spins, with an alkali vapor serving as a mediator. If successful, this could leverage the hour-long coherence time of noble-gas spins for extreme quantum optics and sensing applications.

Protein machines carry out specific tasks in the cell by alternating chemical steps with conformational/structural transitions. Single-molecule fluorescence spectroscopy is a powerful tool for exposing large-scale function-related motions. We recently developed a sophisticated maximum likelihood algorithm for the analysis of single-molecule experiments, which can track conformational dynamics even on the microsecond time scale. In the lecture, I will show how this novel analysis helped us understanding the dynamics of two machines, an abundant enzyme and a protein that rescues other proteins from aggregation. 

Tracing the evolution of baryonic matter from atoms in space to stars
such as our Sun hinges on an accurate understanding of the underlying
physics controlling the properties of the gas at every step along this
pathway. Here I will explain some of the key epochs in this cosmic cycle
of gas and highlight our laboratory studies into the underlying atomic,
molecular, plasma, and surface processes which control the observed
properties of the gas.

Deep artificial neural networks (DNNs) have been driving many of the
recent advancements in machine learning. An important question on the
theory side of DNNs concerns the role played by each layer in the
network. Recently two bold conjectures were made: The first is that
DNNs learn to perform a series of Renormalization-Group (RG)
transformations on the data they are given. The second claims that
each subsequent layer in a DNN increases more and more a certain
conditional-entropy. In this talk, I’ll discuss some tests and
refinements of these two conjectures. In particular, I’ll present an
information-theory based formulation of real-space RG and compare it
with more conventional training algorithms for DNNs. Time permitting
I’ll also discuss the training of DNNs using the above
conditional-entropy based goal.


Relevant papers
[1] M. Koch-Janusz and Z.R. (2018)
https://www.nature.com/articles/s41567-018-0081-4
[2] Z.R. and R. A. de Bem (2017) https://openreview.net/forum?id=BJGWO9k0Z
[3] P. M. Lenggenhager, Z.R.,S. D. Huber, M. Koch-Janusz (2018)
https://arxiv.org/pdf/1809.09632.pdf

By combining the theory of incompatible elastic sheets with chemical analysis we introduce a new paradigm for the modeling and analysis of nano-scale self-assembled solid sheets. Analysis of molecular interactions provides inputs to the elastic model, which determines the supramolecular structure and its thermal fluctuations.

The approach is demonstrated in a combined experimental-theoretical study of nano-scale self-assembled ribbons, made of lipids and peptides with chiral head groups. We analytically derive quantitative predictions for ribbons configurations and shape fluctuations. These are confirmed experimentally, revealing unusual mechanics and statistics, indicating that the shape and mechanics of the suprasturactures are governed by geometrical incompatibility.

Hawking radiation has been one of the intellectually most influential predictions of theoretical physics, connecting general relativity with quantum mechanics and thermodynamics, but it has never been fully observed yet, even in laboratory analogues, despite admirable experimental progress made. Here we report on clear, non-ambiguous measurements of stimulated Hawking radiation in nonlinear fiber optics. Our experiment shows the surprising robustness of the Hawking effect in optics and may finally clear the path towards a full quantum demonstration.

Cracks, the major vehicle for material failure, undergo various dynamic instabilities in brittle materials. Despite their fundamental importance and apparent similarities to other instabilities in condensed-matter and materials physics, these instabilities remain poorly understood. In particular, they are not explained by the classical theory of cracks, which is based on the linearized field theory of elasticity. We develop a 2D theory capable of predicting arbitrary paths of dynamic cracks, incorporating small-scale, near crack-tip elastic nonlinearity. We show that cracks undergo a high-speed oscillatory instability controlled an intrinsic nonlinear elastic length, in quantitative agreement with experiments. The instability is shown to exist, with the same salient properties, in materials exhibiting widely different near crack-tip elastic nonlinearity, highlighting its universal character. We further show that upon increasing the driving force for fracture, a tip-splitting instability emerges, which is experimentally demonstrated. The theory culminates in a comprehensive stability phase diagram of 2D brittle fracture.

Physical Hamiltonians are not Hermitian (NH) when either the potentials are complex (as for example in optics when the index of refraction is complex) or when the potential is real but the system is in a metastable state (as for example in alpha decay or in an autoionization/photoionization of atoms and molecules). Physical phenomena that it is hard and often impossible to study by standard (Hermitian) quantum mechanics (QM) will be discussed. The focus will be on the discovery of physical phenomena that can be described in a simple way solely by the mean of NHQM.

Whenever two surfaces are at nanometer separation, as when they are in or close to contact, even small potential differences (<0.5V) between them may result in extremely large electric fields (of order 10⁸ V/m) across the intersurface gap. Such large fields can readily affect interfacial phenomena. My talk will describe recent results where interactions between a molecularly smooth mica surface and a gold surface at variable potentials are measured directly, shedding light on different phenomena from the charging dynamics of an individual nanopore to a remarkable control of friction through surface potential changes.

Super-oscillating functions are band-limited functions that oscillate
locally faster than their higher Fourier component. These functions were
studied in the past for wide ranging applications, including super-directive
antennas, weak measurements of quantum systems, imaging and microscopy. 
Here I will present new applications of super-oscillations for trapping and
manipulation of nano-particles, for generation of electron beams with
sub-diffraction central spot, for realization of nonlinear frequency
converters with arbitrary narrow spectral and thermal bandwidth, and finally
for structured illumination microscopy.

Neurons are the computational elements that compose the brain and their fundamental principles of activity are known for decades. According to the long-lasting computational scheme each neuron functions as a threshold unit. Each neuron sums the incoming electrical signals via its dendrites and when the membrane potential reaches a certain threshold the neuron typically generates a spike to its axon. We present three types of experiments, local and nonlocal time interference, using neuronal cultures, indicating that each neuron functions as a collection of independent threshold units, where the neuron is anisotropically activated following the origin of the arriving signals to the membrane.Finally, dendritic learning as a paradigm shift in brain learning will be briefly discussed. Results call to re-examine neuronal functionalities beyond the traditional framework, and the advanced computational capabilities and dynamical properties of such complex systems. 

  The cosmic radio spectrum is expected to show a strong absorption signal around redshift 20 that corresponds to the rise of the first stars; specifically, the stellar radiation turns on 21-cm absorption by atomic hydrogen. The EDGES global 21-cm experiment has detected the first such signal, finding a stronger absorption than the maximum expected. This absorption can be explained by invoking excess cooling of the cosmic gas induced by an interaction with dark matter. This would have far reaching consequences, including an upper limit on the mass of dark matter particles that conflicts with the expectations for WIMPs. Specific particle physics models are highly constrained, but observations will decide. In particular, we predict that 21-cm fluctuations at cosmic dawn could be much larger than previously expected, exhibiting a specific signature of dark matter.

Entanglement, which expresses non-local correlations in quantum mechanics, is the fascinating concept behind much of toady`s aspiration towards quantum technologies. Nevertheless, directly measuring the entanglement of a manyparticle system is very challenging. We shall present a proposal to use an artificial intelligence system based on supervised machine learning by a convolution neural network (CNN) to infer the entanglement from a measurable observable for a disordered interacting quantum many-particle system. Several structures of neural networks are tested and a deep CNN akin to structures used for image and speech recognition will be shown the best performance. After training on a set of 500 realizations of disorder, the network is applied on 200 new realizations and its results for the entanglement entropy (EE) where compared to a direct calculation of the EE. Excellent agreement was found, except for several rare region which in a previous study were identified as belonging to an inclusion of a different quantum phase associated with the Griffiths phase.

Most of the organic molecules, the basic building blocks of life, are transparent to visible light, except for a small group of molecules known as biochromophores. Biochromphores are responsible for vision, photo-synthesis (the process of harvesting solar energy), for exotic phenomena such as bioluminescense (for example in fireflies and jelly-fish) and for all the colors we see in nature. In this talk we will explore how tools developed originally for the study of nuclear and atomic physics provide an insight into the workings of these important molecules, and the basic quantum mechanical principles governing their behavior.

We will focus on the case of the retinal chromophore, which is the photon detector used in every known form of animal vision. We will show how the color of the chromophore can be tuned by its surrounding environment, which is critical for color vision. We will also discuss how to directly observe structural changes of the retinal chromophore using ion mobility spectroscopy.

Efficient polarization of organic molecules is of extraordinary relevance when performing nuclear magnetic resonance (NMR) and imaging. Commercially available routes to dynamical nuclear polarization (DNP) work at extremely low temperatures, relying on the solidification of organic samples and thus bringing the molecules out of their ambient thermal conditions. In this talk I will review recent results of polarization transfer from optically pumped nitrogen vacancy centers in diamond to external molecules at room temperature.  These results set the route to hyperpolarization of diffusive molecules in different scenarios and consequently, due to an increased signal, to high-resolution NMR and MRI.

Optical phenomena visible to everyone abundantly illustrate important

ideas in science and mathematics. The phenomena considered include

rainbows, sparkling reflections on water, green flashes, earthlight on the

moon, glories, daylight, crystals, and the squint moon. The concepts

include refraction, wave interference, numerical experimen,

asymptotics, Regge poles, polarization singularities, conical intersections,

and visual illusions.

While the equilibrium properties, states, and phase transitions of interacting systems are well described by statistical mechanics, the lack of suitable state parameters has hindered the understanding of non-equilibrium phenomena in divers settings, from glasses to driven systems to biology. Here we introduce a simple idea which enables the quantification of organization in non-equilibrium and equilibrium systems, even when the form of order is unknown. The length of a losslessly compressed data file is a direct measure of its information content, Ic , which, when the file represents a microstate in equilibrium, is its entropy. I will discuss Ic for some out-of-equilibrium systems, and show that it both identifies ordering and reveals critical behavior in dynamical phase transitions. 

Quantum Hall systems are the simplest examples of topological insulators. The bulk of a quantum Hall system has a gap to all charged excitations, and all charge conduction occurs at the edges. Typically, these edges are chiral, they carry current only in one direction. In real samples, as the confining potential at the edge is softened, the edges can undergo reconstruction, which means the number and chirality of the edge modes can change, despite the bulk being inert. I will discuss the general phenomenon of reconstruction, which is driven by electrostatic considerations, and end with an example of a novel type of reconstruction in which exchange, rather than electrostatics, plays the dominant role.

See attached

Despite its great success in describing the elementary particles and interactions among them, the Standard Model (SM) fails to explain certain phenomena: it does not include gravity, it accommodates neither neutrino masses nor dark matter, and it predicts a minuscule baryon asymmetry. These shortcomings indicate that the SM needs to be extended. Many models extending the SM have been developed over the years and the search for signatures predicted by these models is at the core of the physics program of two of the LHC experiments, ATLAS and CMS, at CERN. 

So far, after over seven years of data taking, no indication for physics beyond the SM (BSM) was observed. Could we be missing something? In this talk, I will review some of the main actions we take in order to guarantee that if BSM physics is produced at the LHC it will not escape detection.

Dark matter has been a major paradigm in cosmology for the past five decades, with evidence mounting and becoming ever more convincing over the years. However, all the observations of this elusive matter are based on gravitational systems. Many efforts to determine the particle or field nature of the dark matter were carried out, but so far without success. In my talk I will go through the evidence and basic notions related to dark matter, and will then focus on one of the most promising channels for its understanding - direct searches for dark matter. I will present the current state of affairs, with the world's most sensitive detector, XENON1T, and then discuss the future of the filed, with planned experiments and small scale R&D.

This talk will address the preferred mass and time for galaxy formation, in dark-matter haloes similar to the one that hosts the Milky way but when the Universe was only a few Gigayears old. It is proposed that this magic scale arises from the interplay between supernova explosions in low-mass galaxies and feedback from super-massive black holes in massive galaxies, associated with shock heating of the circum-galactic gas which suppresses cold gas supply for star formation in massive galaxies. Cosmological simulations reveal that the same mechanisms are responsible for a robust sequence of events in the history of typical galaxies, were galaxies undergo a dramatic gaseous compaction, sometimes caused by galaxy mergers, into a compact star-forming phase, termed “blue nugget”. This process triggers inside-out quenching of star formation, which is maintained by a hot massive halo aided by black-hole feedback, leading to todays passive elliptical galaxies. The blue-nugget phase is responsible for drastic transitions in the main galaxy structural, kinematic and compositional properties. In particular, the growth of the black hole in the galaxy center, first suppressed by supernova feedback when below the critical mass, is boosted by the compaction event and keeps growing once the halo is massive enough to lock the supernova ejecta by its deep potential well and the hot halo. These events all occur near the same characteristic halo mass, giving rise to the highest efficiency of galaxy formation and black-hole growth at this magic mass and time.

Ordinary nonlinear optical processes in x-ray regime are known to be very weak, while conventional x-ray sources suffer from insufficient brightness. Nevertheless, recent and expected improvements in brightness and beam quality of x-ray sources, together with new facilities such as the x-ray free-electron laser, offer the possibility of extending the concepts of nonlinear and quantum optics into x-ray energies. The new facilities with their increased power allow the observation of new x-ray nonlinear and quantum effects. Indeed, recently, the number of demonstrations of nonlinear and quantum effects in the x-ray regime, is growing rapidly. I will describe recently performed and proposed nonlinear experiments at x-ray wavelengths including x-ray and visible wave mixing [1], x-ray second harmonic generation [2] and x-ray parametric down-conversion into the ultraviolet and optical regimes [3,4]. I will discuss future directions of implementing nonlinear x-ray techniques as tools for spectroscopy and studies of ultrafast effects. For example, x-ray and visible mixing may lead to atomic scale resolution techniques to study chemical bonds. X-ray parametric down-conversion can be developed into techniques to study properties such as Fermi energies, plasmons, and the density of states in crystals. Nonlinear techniques are expected to be useful in the inspection of subfemtosecond temporal pulses.

[1] T. E. Glover et al. Nature 488, 603 (2012).

[2] S. Shwartz et al. Phys Rev. Lett. 112, 163901 (2014)

[3] D. Borodin , S. Levy , and S. Shwartz, App. Phys. Lett. 110, 131101 (2017).

[4] A. Schori et al. Phys. Rev. Lett. 119, 253902 (2017)

Rogue waves are frick waves suddenly appearing and can endanger life and cargo. For many years no one believed that such waves exist and any stories about it were considered as fairy tales. Recently, such waves were discovered in different mediums and specifically in optics. We discovered a new type of rogue waves and measured it with high resolution. In the talk, we will present the mechanism behind rogue waves in general and specifically our type of rogue waves.   

We realize experimentally an information machine converting information to work. Our experimental design is comprised of a colloidal particle diffusing in a microfluidic channel, with a repelling laser based barrier that is moved in feedback to the measured particle position. In a quasi-static mode of operation, the amount of used information is related to the Shannon entropy of uncorrelated steps. We develop a scheme to calculate this information at steady state at fast operation, which induces temporal correlations. We use this calculation to characterize the output power and efficiency of our information machine as a function of feedback cycle time.

Realizing imaging of atomic motion de-novo within multiple molecular bonds in isolated molecules, with Angstrom and femtosecond resolutions is a grand challenge for the atomic molecular and optical physics community.  We will present several recent results in imaging quantum dynamics at the atomic length and time scales using ultrafast coherent x-ray diffraction at free electron lasers, photoelectron self-diffraction via strong field ionization, coincidence techniques, and advanced imaging and data analysis schemes that create such molecular movies without prior information of the system under study.  Time-resolved femtosecond x-ray diffraction patterns from laser-excited molecular iodine were used to create high fidelity molecular movies de-novo. We imaged electronic population transfer, vibrational motion, dissociation, rotational dephasing, Raman transitions, and non-adiabatic population transfer via coherent mixing of different electronic states.  We’ll also discuss results from photoelectron velocity map imaging and coincidence techniques as potential routes for table-top molecular movies. Finally, we will discuss using novel experimental and analysis methods, extending to the condensed phase and to systems of increased complexity.

Scale invariance is a common property of our everyday environment. Its
breaking gives rise to less common but beautiful structures like fractals.
At the quantum level, breaking of continuous scale invariance is a
remarkable exemple of quantum phase transition also known as scale
anomaly. The general features of this transition will be presented at an
elementary quantum mechanics level. Then, we will show recent experimental
evidence of this transition in graphene.

I will start with an overview of some of the most important open
questions in particle physics. Some of these issues require, and other
strongly suggest, the existence of yet-unknown particles and fields in
nature. I will argue that the Standard Model is just an effective
partial description of a more fundamental theory that stands behind it
and is yet to be discovered. I will then focus on the puzzle of the
electroweak-Planck hierarchy, where hints about the underlying
mechanism are likely to be within the reach of the Large Hadron
Collider (LHC) at CERN. I will also mention my own work, which
involves analyzing the results of LHC searches and proposing new
search directions for the physics behind the electroweak-Planck
hierarchy and other new phenomena that may be accessible at the LHC.

The Nobel Prize in Physics 2015 was given to the leaders of two experiments that discovered neutrino flavor transitions. This discovery shows that neutrinos have mass. I will describe the experiments and their results, and explain the implications for theory and their significance.

Under certain conditions, it takes a shorter time to cool a hot system than to cool the same system initiated at a lower temperature. This phenomenon — the “Mpemba effect” — was first observed in water and has recently been reported in other systems. Whereas several detail-dependent explanations were suggested for some of these observations, no common underlying mechanism is known. We present a widely applicable mechanism for a similar effect, the Markovian Mpemba effect, derive the sufficient conditions for its appearance, and demonstrate it explicitly in the anti-ferromagnet Ising model. Interestingly, the Markovian Mpemba effect can be classified as ``weak'' or ``strong'' and as ``direct'' or ``inverse''. In the Ising model we show that the ``strong'' (direct and inverse) effect exists even in the thermodynamic limit.

The governing role of hydrophobic interactions in countless biological phenomena and technological systems, including protein folding, transmembrane proteins, cell membranes, detergents, paints, decontamination of pollute water, and more, has motivated extensive theoretical and experimental efforts aimed at deciphering the microscopic foundations of this interaction. Yet, after more than a century of extensive research a full predictive theory of this elusive phenomenon is still missing, largely due to the lack of suitable experimental techniques capable of probing the interface between hydrophobic surfaces and water at high enough resolution. In the talk, I will present our recent explorations of this interface using an ultra-high resolution atomic force microscope built in-house for the task and disclose compelling evidence that the hydrophobic interaction reflects a phase transition taking place in the medium when two hydrophobic surfaces approach each other to within a few nanometers. Along the way I'll demonstrate the sub-atomic resolution of our microscope and its value for the study of water structure near surfaces and biomolecules.

Quantum theory is the strangest theory ever introduced into science.  Everyone knows how to make calculations using quantum theory and the calculations always agree with experiment.  But questions remain regarding what this theory is telling us about nature.  This is called the “interpretation of quantum theory.”  The most widely accepted interpretation of quantum theory is the Copenhagen interpretation.  I will discuss the Copenhagen interpretation, point out its defects, and present an alternative interpretation which does not suffer from these defects.

Over the past 2 decades, our understanding of how cosmic rays affect the terrestrial cloud cover has evolved from rough empirical evidence to an almost complete physical picture. This link helps us understand many of the past climate variations—from days to Eons, including for example the appearance of ice age epochs on Earth and 20th century global warming. In this talk I will review the evidence including recent breakthroughs in our atmosphere mimicking lab, which pin point the two physical mechanisms increasing linking between atmospheric charge and the formation of cloud condensation nuclei. I will also discuss resent results on how the cosmic ray climate link can be used to determine the amount of Dark Matter at the galactic plane.

Bacterial swarming is a collective mode of motion in which cells migrate rapidly over surfaces. Swarming is typically characterized by densely packed groups moving in coherent patterns of whirls and flows. Recent experiments showed that within such dense swarms, bacteria are performing super-diffusion that is consistent with a Levy walk. The talk will explain this observation and present a simple model suggesting that chaos and Levy walking are a consequence of group dynamics. The model explains how cells can fine-tune the geometric properties of their trajectories.

In the vast majority of superconductors, the Cooper pairs are formed from electrons with an antiparallel spin alignment and are in the spin-singlet state. In contrast, there are very few materials that show evidence for the exotic state of triplet superconductivity, in which the Cooper pairs comprise electrons with parallel spins. Such a state was predicted to emerge, under some conditions, at superconductor-ferromagnet (S-F) interfaces, and may be important for superconducting-spintronic devices. First experimental evidence for triplet superconductivity was provided by observations of long-range (much larger than the coherence length in F) spin-polarized supercurrents in S-F-S devices. To address this problem from a different angle, we employed scanning tunneling spectroscopy (STS) on various S-F bilayer systems, and our tunneling spectra reveal long-range penetration of superconducting correlations into the ferromagnet, consistent with spin-aligned triplet-pairing with a p-wave order-parameter symmetry. I will also discuss two other systems that showed clear signatures of p-wave triplet-superconductivity in the tunneling spectra. The first consists of a-helix chiral molecules deposited on Nb (a conventional superconductor), and the second comprises single layer graphene deposited on the electron-doped cuprate superconductor Pr_1.85Ce_­CuO₄.  

Studying the transition of properties of nanostructures as they develop from the zero-dimensional to the one-dimensional regime is significant for unravelling the modifications that occur in the electronic structure of the particle as its length to width aspect ratio is increased. Such understanding can lead to better design and control of the particle properties, with relevance for a wide range of technological applications and in particular for flat panel displays, where semiconductor nanocrystals are presently used to achieve greatly improved color quality with energy saving characteristics. The high degree of control of shape and morphology of nanoparticles in colloidal synthesis, which allows forming structures of similar composition but of different dimensionalities and shapes, open the way for probing such dimensionality effects. We will present several effects involving the 0D to 1D transition in semiconductor nano heterostructures of different morphologies including “sphere in a sphere”, “sphere in a rod” and “rod in a rod”. Further effects of a graded shell composition, a novel rod-couples architecture and dumbbells morphology will also be described. 

Many real-world complex systems are composed of interacting entities, where their measured activity is a result of underlying complex, usually nonlinear, dynamics. Examples of such network-based dynamical models include: biochemical, ecological and regulatory dynamics. Understanding the underlying dynamics is a key in order to control those systems. Indeed, theory of nonlinear dynamics in mathematics and statistical physics provide deep and detailed understanding of such systems. Yet, the main challenge is that most of the available data comes from snapshots originated in different individuals, and thus is considered as insufficient to extract the actual underlying dynamics, which remain unknown. I will present a novel approach to address this gap between the theory of nonlinear dynamics and the available data from dynamical systems. The approach will be demonstrated on two systems: (i) the human microbiome, the ecological community of microbes living in and on our body, and (ii) gene regulatory networks in human cells. 

Quantum-critical strongly correlated systems feature universal collision-dominated collective transport. Viscous electronics is an emerging field dealing with systems in which strongly interacting electrons flow like a fluid. We identified vorticity as a macroscopic signature of electron viscosity and linked it with a striking macroscopic DC transport behavior: viscous friction can drive electric current against an applied field, resulting in a negative resistance, recently measured experimentally in graphene. I shall also describe current vortices, expulsion of electric field, conductance exceeding the fundamental quantum-ballistic limit and other wonders of viscous electronics. Strongly interacting electron-hole plasma in high-mobility graphene affords a unique link between quantum-critical electron transport and the wealth of fluid mechanics phenomena.

The inherent electronic mismatch between molecules and metals is a general limitation for efficient electron transport in molecule-based electronics, including organic light emitting diodes, nanoscale organic spin-valves, and single-molecule transistors.

In this talk, I will review our recent progress in revealing an upper limit for conductance across metal-single molecule interfaces [1], as well as extreme spin filtering and unusual magneto-transport effects in metal-oxide junctions [2] and half-metallic molecular junctions. These findings can be used to derive general principles for efficient charge and spin transport manipulations at the atomic scale [1-4].

References:

[1] T. Yelin, R. Korytár, N. Sukenik, R. Vardimon, B. Kumar, C. Nuckolls, F. Evers & O. Tal, Nature Materials, 15, 444 (2016).      

[2] R. Vardimon, M. Klionsky & O Tal, Nano Letters, 15, 3894 (2015).

[3] D. Rakhmilevitch, R. Korytár, A. Bagrets, F. Evers & O. Tal, Physical Review Letters 113, 236603 (2014).

[4] D. Rakhmilevitch, S. Sarkar, O. Bitton, L. Kronik & O. Tal, Nano Letters 16, 1741 (2016).

A framework for studying the vulnerability and the recovery of networks of interdependent networks will be presented.

 In interdependent networks, when nodes in one network fail, they cause dependent nodes in other networks to also fail. 

This may happen recursively and can lead to a cascade of failures and to a sudden fragmentation of the system.
I will present analytical solutions for the critical thresholds and the giant component of a network of n interdependent networks.   I will present examples of applying our model to real  interacting networks.

I will also show, that the general theory has many novel features that are not present in the classical network theory. 

When recovery of components is enabled, global spontaneous recovery of the networks and hysteresis phenomena occur

 and the theory suggests an optimal repairing strategy for a system of systems.
I will also show that interdependent networks embedded in space are
significantly more vulnerable compared to non embedded networks. In particular, small localized attacks of zero fraction 

may lead to cascading failures and catastrophic consequences.

Thus, analyzing real data and realistic models of network of networks is highly required to understand the system vulnerability.
 

References:
[1] J. Gao, S. Buldyrev, H. E. Stanley, S. Havlin, Nature Physics, 8, 40 (2012).
[2] A. Bashan et al, Nature Physics, 9, 667 (2013)
[3] A Majdandzic et al, Nature Physics 10 (1), 34 (2014); Nature Comm. 7, 10850 (2016)

[4] Daqing Li, B. Fu, Y. Wang, G. Lu, Y. Berezin, H. E. Stanley, S. Havlin, PNAS 112, 669 (2015)

[5]  J. Zhao, Daqing Li, H. Sanhedrai, R. Cohen, S. Havlin, Nature Comm. 7, 10094 (2016)  

In 1964 V. L. Ginzburg predicted that new superconducting phases could appear in ultrathin films deposited on insulating surfaces. In 2010 superconductivity below 2K was discovered in some crystalline atomic monolayers of Pb grown on atomically clean Si(111) [1, 2]. Though, the amorphous Pb monolayer was found non-superconducting, but rather a correlated metal. Interestingly, Pb-monolayers can be on-demand made amorphous or crystalline, with or without presence of bulky superconducting Pb-nano-islands. This makes the Pb/Si(111) system useful to probe superconducting correlations in the vicinity of S-N or S-S’ interfaces by STM [3,4].

When two superconducting Pb-islands are linked together by a few nanometer wide non-superconducting amorphous atomic layer of Pb, superconducting correlations may propagate between the two islands, allowing a dissipation-less Josephson current to flow through the link. In the presence of a magnetic field, the Josephson vortices are expected to appear in such S-N-S Josephson junction. Josephson vortices are conceptual blocks of advanced quantum devices such as coherent terahertz generators or qubits for quantum computing, in which on-demand generation and control is crucial.

In our lecture we describe a series of recent experiments which mapped superconducting correlations in the vicinity of S-N junctions [3,4] as well as inside SNS proximity Josephson junctions using scanning tunneling microscopy [5]. By following the Josephson vortex formation and evolution we demonstrate that they originate from quantum interference of Andreev quasiparticles, and that the phase portraits of the two superconducting quantum condensates at edges of the junction decide their generation, shape, spatial extent and arrangement [5].

[1] T. Zhang, et al. Nature Phys. 6, 104–108 (2010).

[2] Ch. Brun, et al. Nature Phys. 10, 444 (2014).

[3] L. Serrier-Garcia, et al. Phys. Rev. Lett. 110, 157003 (2013).

[4]V.Cherkez, et al. Phys. Rev. X 4, 011033 (2014).

[5] Roditchev D., et al. Nature Phys. 11, 332 (2015).

Friction is generally described by a single degree of freedom, a ‘friction coefficient’. We experimentally study the space-time dynamics of the onset of dry and lubricated frictional motion when two contacting bodies start to slide. We first show that the transition from static to dynamic sliding is governed by rupture fronts (closely analogous to earthquakes) that break the contacts along the interface separating the two bodies. Moreover, the structure of these "laboratory earthquakes" is quantitatively described by singular solutions originally derived to describe the motion of rapid cracks under applied shear. We demonstrate that this framework quantitatively describes both earthquake motion and arrest. A further surprise is that lubricated interfaces, although “slippery”,  actually becomes tougher; lubricants significantly increase dissipated energy during rupture. The results establish a new (and fruitful) paradigm for describing friction.

Morphogenesis, the emergence of well-defined patterns of functional tissues during development, is carried out by the collective dynamics of multiple physical and biochemical processes at different levels of organization, from local molecular events to large-scale chemical, electrical and mechanical stress fields. Morphogenesis emerges by the interaction of these various processes, which must evolve simultaneously as coupled fields. We take advantage of a unique multicellular organism, Hydra, famous for its extraordinary regeneration capabilities, to advance our biophysical understanding of morphogenesis. I will discuss our recent experiments on Hydra regeneration, shedding light on the role of the actomyosin cytoskeleton and the forces it generates during morphogenesis. We apply mechanical constraints by studying regeneration from tissue segments anchored on wires, showing that the wires induce order in morphogenesis. Finally, we utilize external force fields, hydrodynamic flows, electric fields and magnetic forces on beads attached to the regenerating tissue, to induce spatio-temporal modes during the regeneration process. Perturbing the regeneration process and imposing external constraints enable us to expose alternative developmental trajectories.

Spin based properties, applications, and devices are commonly related to magnetic effects and to magnetic materials. However, we found that chiral organic molecules act as spin filters for photoelectrons transmission [1]  in electron transfer [2] and in electron transport [3]  .

The new effect, termed Chiral Induced Spin Selectivity (CISS) [4,5]  has interesting implications for the production of new types of spintronics devices [6]  and on electron transfer in biological systems.  The effect was found in bio-molecules and in bio-systems [7]. The basic effect will be explained and various applications and implications will be discussed.

1. Göhler, B.; Hamelbeck, V.; Markus, T.Z.; Kettner, M.; Hanne, G.F.; Vager, Z.; Naaman, R.; Zacharias,  H. Science 2011, 331, 894.
2. Mishra, D.; Markus, T.Z.; Naaman, R.; Kettner, M.; Göhler, B.; Zacharias, H.; Friedman, N.; Sheves, M.; Fontanesi, C. PNAS,   2013, 110, 14872.
3.  Xie, Z.; Markus, T. Z.; Cohen, S. R.; Vager, Z.; Gutierrez, R.; Naaman, R. Nano Letters, 2011, 11, 4652.
4. Naaman, R.; Waldeck, D.H. J. Phys. Chem. Lett. (feature) 2012, 3, 2178.
5. R. Naaman, D. H. Waldeck, Spintronics and Chirality: Spin Selectivity in Electron Transport Through Chiral Molecules, Ann. Rev. Phys. Chem. 2015, 66, 263–81.
6. Ben Dor, O.; Yochelis, S.; Mathew, S. P.; Naaman, R.; Paltiel, Y. Nature Communication, 2013, 4, 2256.
7.  I. Carmeli, K. S. Kumar, O. Hieflero, C. Carmeli, R. Naaman,  Angew. Chemie  2014, 53, 8953 –8958.

Few years ago it was suggested by S. Tan that the properties of cold and dilute quantum gases depend on a new characteristic quantity, the ``contact''. The ``contact'' describes the probability of two particles coming close to each other, i.e. it is a measure of the number of close particle pairs in the system. Utilizing this concept, a series of theorems, already verified experimentally, predicts the macroscopic properties of the system. In my talk I will present Tan’s  ``contact'' and its generalization to nuclear systems, introducing the various nuclear contacts, and their applications.
 

Mass transfer between members of a binary is a common and well studies situation. As members of a binary become closer to each other, mass may leak from one object due to the strong tidal forces from the other. Usually, the leaking mass flows towards the companion, but we show that for main sequence stars that orbit the supermassive black hole in the galactic center and emit gravitational waves mass may also leak away from it. We show that the mass transfer affects the evolution of the gravitational wave emission in a way that reflects internal properties of the star. This may be relevant to observations of the planned LISA mission. On another front, tides may lead to orbital decay of planets which are close enough to their stars. Mass transfer will occur and we discuss its observational consequences in view of data from the Kepler mission.

גורמי מחלות (פתוגנים), מזיקים ועשבים גורמים נזקים רבים לגידולים חקלאיים והם פוגעים ביכולתנו לספק מזון בעולם שאוכלוסייתו גדולה ואשר בו יותר מ-800 מליון רעבים. הדברת גורמי הפגע מאפשרת העלאת היבולים. השימוש בחומרי הדברה (pesticides) הוא דרך מאוד יעילה להדברת הפגעים הללו אך השימוש בהם עלול לפגוע בסביבה ובבריאות. נעשים מאמצים לפתח  חלופות לחומרי הדברה שהן ידידותיות לסביבה אך גם יעילות בהדברה. פיתוח זני צמחים עמידים גנטית למחלות, הדברה ביולוגיות של פגעים ושיטות אחרות הנן חלופות שנחקרות וחלקן בשימוש נרחב.

בארץ פותחה שיטת החיטוי הסולרי (Soil solarization) של חימום הקרקע באמצעות יריעות פוליאתילן שקופות להדברה פתוגנים ועשבים ע"י קטילה תרמלית של הפתוגנים כחלופה לחיטוי כימי של הקרקע אשר נעשה בדרך כלל באמצעות חומרים רעילים. נערכו מחקרים רבים בארץ ובעולם (ביותר מ-70 מדינות) על היבטים מיקרוביאליים, פיסיקליים, כימיים, אגרוטכניים, טכנולוגיים, כלכליים ועוד של החיטוי הסולרי במטרה לשפר את יעילותו ולהרחיב את השימוש בו למטרות נוספות, מעבר לחיטוי קרקע.

שימו לב: ההרצאה תנתן בעברית. המרצה - חתן פרס ישראל בחקר החקלאות ומדעי הסביבה משנת תשע"ד.

In his famous lectures, R. P. Feynman highlights the deep unity of physics and the analogies existing between sometimes vastly different physical systems. In the same spirit I will demonstrate how the tools and concepts inherited from classical hydrodynamics can be used to explain the quantum world. As an example, I will show that the same phenomena govern the physics of water-walking insects and that of laser-cooled superfluid vapours.

Attosecond science is a young field of research that has rapidly evolved over the past decade. Performing time-resolved measurements with attosecond precision is a significant challenge. The rapid progress in this field opened a door into a new area of research that allows one to observe multi-electron dynamics. Currently, two main approaches have been successfully demonstrated. The first approach, Attosecond Pump-Probe Spectroscopy, applies an attosecond pulse to initiate or probe a fast-evolving process. An alternative approach, Attosecond Self-Imaging, applies the attosecond production process, to perform the measurement.

Although attosecond spectroscopy holds great promise for both measurement and control of matter, the understanding and implementation of most processes pose significant challenges. The extreme nonlinear nature of the interaction offers numerous channels, strongly coupled by the strong laser field, in which electronic dynamics can evolve.

In the talk I will review some of the main challenges and goals in the field of attosecond science. I will describe advanced schemes in attosecond spectroscopy where the interaction is probed via several synchronized fields. Such integration probes the multidimensional nature of the interaction, thus revealing its complexity. I will then focus on a new direction that integrates the two main branches in attosecond spectroscopy – the attosecond pump-probe scheme with the self-imaging approach.  This scheme increases the dimensionality in both the measurement and control of attosecond scale processes, allowing the observation of a wide range of multielectron phenomena.

Noise analysis in biological systems has greatly increased our understanding of the underlyingcellular processes. Noise in the cell division process is often assumed to be responsible for variability in cell cycle duration, and to underlie heterogeneous responses of bacteria to antibiotics, as well as of cancer cells to drugs.

We show that variability of growth in bacteria can evolve under fluctuating environment.  

More generally, we ask whether we can differentiate between stochastic and deterministic control of cell division variability. Using long-term time lapse microscopy to follow thousands of divisions and tools from non linear dynamics analysis, we show that the variability in cell-cycle duration in mammalian cells, which at first glance seems dominated by noise, is in fact controlled by a deterministic factor.

In this talk I will review the concept of topological superconductivity, of the associated Majorana fermions, and of their recent realization using nanowires in proximity to conventional superconductors. I will then analyze the way that two dimensional Josephson junctions may be employed to create one dimensional topological superconductors and describe the unique properties of the resulting system. 

The standard paradigm for transport in metals relies on the existence of quasiparticles. Transport coefficients such as electrical and thermal conductivities can then be calculated using e.g. Boltzmann equations. However, such an approach fails in the so-called `bad metal' regime, when the quasiparticle mean free paths become comparable to the wavelengths of the electron and/or highest frequency phonon. Transport in non-quasiparticle regimes requires a new framework and has become a subject of intense theoretical and experimental efforts in recent years.  In particular, the diffusivity was singled out as a key observable for incoherent non-quasiparticle transport, possibly subject to fundamental quantum mechanical bounds. Following a review of previous experimental results on bad metallic behavior, we will introduce new results on transport in strongly correlated electron systems with strong electron-phonon interaction. These results suggest that when neither well-defined electron nor phonon quasiparticles are present, thermal transport exhibits a collective behavior of a `soup' of strongly coupled electrons and phonons which diffuses at a unique velocity, exhibiting a saturated scattering time of ~ħ/kT.