The life & flow of polarons: from nonequilibrium formation and relaxation to equilibration in the thermodynamic limit

Abstract: Polarons, quasiparticles composed of an electronic excitation and the material deformation these cause in a solid or liquid, are ubiquitous. Understanding and controlling their formation, nonequilibrium relaxation, and motion are essential in developing next-generation photocatalysts, energy conversion devices, and even superconductors. In this talk, I introduce some of our recent theoretical advances that enable us to probe the exact quantum dynamics of Holstein polarons subject to dispersive phonon baths in small lattice models to the thermodynamic limit. While we illustrate these advances on canonical polaron models, they are broadly applicable to large families of dissipative lattice Hamiltonians with short-range interactions. Physically, we find that polarons can display long nonequilibrium periods of anomalous transport caused by dynamics-induced heterogeneity, even in perfectly homogeneous systems. We explain this finding in the context of the time required for the system to move beyond the far-from-equilibrium regime and into the linear response nonequilibrium regime. These findings also enable us to explain subtle differences between equilibrium (Green-Kubo) and nonequilibrium methods for predicting polaron transport and their different sensitivities to material topology. Our findings can be used to elucidate recent experiments in the formation and transport of polarons in transition metal oxides.