Dynamics of orbital angular momentum in confined geometries and the control of THz magnons in antiferromagnets

I will present recent results on the transport of orbital angular momentum and on the control of THz magnons in antiferromagnets. A key result in the first part is that the effective orbital angular momentum decay rate follows a Dykonov-Perel-scaling and is inversely proportional to the electron scattering rate, even if the latter is small. We show that non-Ohmic flows and spatially varying electric fields result in contributions to the OHE which are distinct from the well known intrinsic and extrinsic mechanisms, including non-local and vorticity induced accumulations of orbital angular momentum. In the second part, I demonstrate that difficult to access antiferromagnetic resonances in the THz range can be parametrically excited with signals at optical frequencies via a mechanism that is called Modulated Floquet Parametric Driving (MFPD). I discuss spin pumping and the formation of entangled, two-mode squeezed magnon pairs in anisotropic antiferromagnets under MFPD. Furthermore, I will show that MFPD induces transitions to symmetry breaking steady-states in which dynamical spin patterns are formed by resonant magnon pairs.