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Physical Review Research

Extended regime of metastable metallic and insulating phases in a two-orbital electronic system

Matteo Vandelli, Josef Kaufmann, Viktor Harkov, Alexander I. Lichtenstein, Karsten Held, E. A. Stepanov

Published Apr 25, 2023• 15 citations
Publisher

Abstract

Taking the nonlocal collective electronic fluctuations into account completely changes the state-of-the-art scenario for the metal-insulator transition in a quarter-filled two-orbital Hubbard model. These fluctuations redistribute the spectral weight between the orbitals, which results in an extremely broad coexistence region between the metallic and Mott insulating states.

DOI
10.1103/physrevresearch.5.l022016

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We study the nonequilibrium dynamics of a simple model for V2O3{\mathrm{V}}_{2}{\mathrm{O}}_{3}V2​O3​ 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 subbands; (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 nonequilibrium 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 nonthermal 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.
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