Phase Separation close to the density-driven Mott transition in the Hubbard-Holstein model

TL;DR

This paper investigates how electron-phonon interactions influence the density-driven Mott transition in the Hubbard-Holstein model, revealing phase separation and polaronic phases through dynamical mean-field theory.

Contribution

It demonstrates that intermediate electron-phonon coupling induces a first-order transition with phase separation, and identifies the emergence of a polaronic phase at higher couplings.

Findings

First-order transition with phase separation at intermediate coupling.

Enhanced metallic compressibility near transition.

Emergence of polaronic phase at larger couplings.

Abstract

The density driven Mott transition is studied by means of Dynamical Mean-Field Theory in the Hubbard-Holstein model, where the Hubbard term leading to the Mott transition is supplemented by an electron-phonon (e-ph) term. We show that an intermediate e-ph coupling leads to a first-order transition at T=0, which is accompanied by phase separation between a metal and an insulator. The compressibility in the metallic phase is substantially enhanced. At quite larger values of the coupling a polaronic phase emerges coexisting with a non-polaronic metal.