Stability of a metallic state in the two-orbital Hubbard model

TL;DR

This paper investigates how electron correlations and Hund coupling influence the stability of metallic and insulating phases in a two-orbital Hubbard model using dynamical mean field theory.

Contribution

It reveals that near-equal intra- and inter-band Coulomb interactions stabilize the metallic state through orbital fluctuations, delaying the Mott transition.

Findings

Fermi-liquid state stabilized near equal intra- and inter-band interactions

System transitions to Mott insulator when interactions differ significantly

Effects of isotropic and anisotropic Hund coupling are analyzed

Abstract

Electron correlations in the two-orbital Hubbard model at half-filling are investigated by combining dynamical mean field theory with the exact diagonalization method. We systematically study how the interplay of the intra- and inter-band Coulomb interactions, together with the Hund coupling, affects the metal-insulator transition. It is found that if the intra- and inter-band Coulomb interactions are nearly equal, the Fermi-liquid state is stabilized due to orbital fluctuations up to fairly large interactions, while the system is immediately driven to the Mott insulating phase away from this condition. The effects of the isotropic and anisotropic Hund coupling are also addressed.