Mott Materials, Correlation Strength, Surfaces and Device Dreams

Electron correlation is responsible for countless interesting condensed matter phenomena. Oxides with electron correlation provide an attractive testbed for many of those, where coupling between the spin, charge and lattice degrees of freedom can be tweaked and explored. Our work started with strontium vanadate (SrVO₃) as a simple test case of the Mott-Hubbard type of correlated electronic structure. We harness advanced thin film synthesis techniques to control the correlation strength by tuning the degree of orbital overlap using picometer-scale lattice engineering. We illustrate how bandwidth control and concurrent symmetry breaking can govern the electronic structure of this SrVO₃ model system [1]. This shows how tensile and compressive biaxial strain oppositely affect the SrVO₃ in-plane and out-of-plane orbital occupancy, resulting in the partial alleviation of the orbital degeneracy. The spectral weight redistribution under strain is derived and explained, illustrating how tensile strain drives the system toward a Mott insulating state. The critical role of the surface chemistry and near-surface region in this picture will be briefly addressed [2,3]. This picture, derived from a simple and clean system, can shed light on other more complex examples.

Pivoting from the simple SrVO₃ system, we studied films of La_1-xSr_xVO₃, a filling-controlled Mott system where the number of free electrons and the electronic phase can be manipulated by the composition. From this system, we crafted a back-gated (solid state) field-effect device with a correlated Mott channel. With this rudimentary device, we demonstrate that with increasing the electron density in the electron channel, the resistance actually increases. This behavior is explained by an increase in the correlation strength due to the increase in electron-electron interaction. The effect on resistivity is ×10 larger than the change in the electron density, and we show that it is likely as high as ×100, due to the screening of the field [4]. We will discuss our vision for crafting this limited demonstrator into a device that might be practical one day.

[1] Shoham et al., Adv. Func. Mat. 33, 2302330 (2023)

[2] Cohen et al., Appl. Phys. Lett. 126, 161602 (2025)

[3] Shoham et al., APL Mat. 12, 051121 (2024)

[4] Shoham et al., APL Mat. 13, 021116 (2025)