Non-equilibrium gap-collapse near a first-order Mott transition

TL;DR

This paper investigates how non-equilibrium electron populations can induce a gap-collapse in a Mott insulator, suggesting a non-thermal pathway to transition into a metallic phase, relevant for materials like V2O3.

Contribution

It demonstrates, using a time-dependent Gutzwiller approach, that excess electrons can trigger a first-order Mott transition via a non-thermal pathway in a simplified model.

Findings

Excess electron population can cause a gap-collapse.

A threshold exists for the transition to occur.

The insulator can become a metastable metal.

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.