Memory in strain-tuned insulator-metal-insulator sequence of transitions after photoexcitation in the Mott material V2O3

Abstract

Memory effects during metal-insulator transitions in quantum materials reveal complex physics and potential for novel electronics mimicking biological neural systems. Nonetheless, understanding of memory and nonlinearity in sequential non-equilibrium transitions remains elusive as the full chain of transitions can involve features lasting anywhere from femtoseconds to microseconds. Here, we extend time-resolved x-ray Bragg diffraction to the dynamic range of timescales spanning 9 orders of magnitude to fully trace the pathways of photoexcited insulator-metal transition and the following relaxation through non-equilibrium metal-insulator transitions in epitaxial films of V2O3, a promising Mott material. We find 5 orders of magnitude variation in metal-insulator transition time, from nanoseconds to hundreds of microseconds, depending on pre-excitation phase state. We provide a theoretical explanation and simulations based on strain feedback to domain nucleation. The lingering transition is stretched in time by memory of spatial and energy heterogeneity and, contrary to known memory effects in vanadium oxides commonly described by power laws, follows an extremely (factor below 0.2) stretched exponential. The induced dramatic slowdown in the light-driven highly correlated system signifies unusually high heterogeneity of transition barriers similar to biological systems, and demonstrates importance of non-local correlations of structure in evolution of transitional phases in quantum materials.