Finite-temperature Mott transitions in multi-orbital Hubbard model

TL;DR

This paper studies how electron interactions cause Mott metal-insulator transitions in multi-orbital Hubbard models at finite temperatures, revealing the influence of orbital degeneracy and fluctuations on the phase diagram.

Contribution

It provides phase diagrams for multi-orbital Hubbard models at finite temperatures using the self-energy functional approach, highlighting the role of orbital fluctuations in Mott transitions.

Findings

First-order transition points depend on orbital degeneracy.

Critical temperature varies with orbital degeneracy.

Orbital fluctuations significantly influence Mott transitions.

Abstract

We investigate the Mott transitions in the multi-orbital Hubbard model at half-filling by means of the self-energy functional approach. The phase diagrams are obtained at finite temperatures for the Hubbard model with up to four-fold degenerate bands. We discuss how the first-order Mott transition points $U_{c1}$ and $U_{c2}$ as well as the critical temperature $T_c$ depend on the orbital degeneracy. It is elucidated that enhanced orbital fluctuations play a key role to control the Mott transitions in the multi-orbital Hubbard model.