Nonequilibrium gap collapse near a first-order Mott transition

Abstract

We study the non-equilibrium dynamics of a simple model for V2O3 that consists of a quarter-filled Hubbard model for two orbitals that are split by a weak crystal field. Peculiarities of this model are: (1) a Mott insulator whose gap corresponds to transferring an electron from the occupied lower orbital to the empty upper one, rather than from the lower to the upper Hubbard sub-bands; (2) a Mott transition generically of first order even at zero temperature. We simulate by means of time-dependent Gutzwiller approximation the evolution within the insulating phase of an initial state endowed by a non-equilibrium population of electrons in the upper orbital and holes in the lower one. We find that the excess population may lead, above a threshold, to a gap-collapse and drive the insulator into the metastable metallic phase within the coexistence region around the Mott transition. This result foresees a non-thermal pathway to revert a Mott insulator into a metal. Even though this physical scenario is uncovered in a very specific toy-model, we argue it might apply to other Mott insulating materials that share similar features.