Single Mott Transition in Multi-Orbital Hubbard Model

TL;DR

This paper investigates the Mott transition in a multi-orbital Hubbard model, revealing a single first-order transition at low temperatures and complex subband behaviors at finite temperatures, reconciling previous conflicting results.

Contribution

It demonstrates that inter-orbital Coulomb interactions cause a single transition, not multiple orbital selective ones, using dynamical mean field theory and quantum Monte Carlo methods.

Findings

Single first-order Mott transition at low temperatures.

Finite temperature subband behavior varies significantly.

Narrow band shows quasi-insulating features near transition.

Abstract

The Mott transition in a multi-orbital Hubbard model involving subbands of different widths is studied within the dynamical mean field theory. Using the iterated perturbation theory for the quantum impurity problem it is shown that at low temperatures inter-orbital Coulomb interactions give rise to a single first-order transition rather than a sequence of orbital selective transitions. Impurity calculations based on the Quantum Monte Carlo method confirm this qualitative behavior. Nevertheless, at finite temperatures, the degree of metallic or insulating behavior of the subbands differs greatly. Thus, on the metallic side of the transition, the narrow band can exhibit quasi-insulating features, whereas on the insulating side the wide band exhibits pronounced bad-metal behavior. This complexity might partly explain contradictory results between several previous works.