Mott transition in multi-orbital systems

TL;DR

This paper investigates the nature of Mott transitions in multi-orbital systems, revealing that inter-orbital Coulomb interactions cause a single transition with varied spectral properties across subbands.

Contribution

It demonstrates that multi-orbital systems undergo a unified Mott transition due to inter-orbital interactions, contrasting with the possibility of orbital-dependent transitions.

Findings

Inter-orbital Coulomb interactions lead to a single Mott transition.

Subbands show different correlation strengths in the metallic phase.

Subbands have different band gaps in the insulating phase.

Abstract

Metal insulator transitions driven by local Coulomb interactions are among the most fascinating phenomena in condensed matter physics. They occur in a large variety of transition metal compounds. Most of these strongly correlated materials consist of valence bands derived from electronic d shells where intra- and inter-orbital Coulomb interactions are equally important and where the crystal structure splits the valence bands into narrow and wide subbands. A fundamental question is whether these systems exhibit a common Mott transition, implying all subbands to be either metallic or insulating, or successive orbital dependent transitions, implying a coexistence region with metallic and insulating behavior present in different subbands. Using the dynamical mean field theory we show that inter-orbital Coulomb interactions lead to a single Mott transition. Nevertheless, the subbands exhibit more or less strongly correlated excitation spectra in the metallic phase and different band gaps in the insulating phase.