Metal-insulator transition in half-filling two-orbital Hubbard model on triangular lattice

TL;DR

This study uses dynamical mean-field theory to analyze the metal-insulator transition in a half-filling two-orbital Hubbard model on a triangular lattice, revealing the transition's order depends on Hund's coupling J.

Contribution

It demonstrates how Hund's coupling influences the order of the metal-insulator transition in a two-orbital Hubbard model on a triangular lattice.

Findings

MIT occurs at specific U_c values depending on J

Transition is first-order for J > 0 and second-order at J=0

Low symmetry with finite Hund's coupling causes first-order transition

Abstract

We have investigated the half-filling two-orbital Hubbard model on a triangular lattice by means of the dynamical mean-field theory (DMFT). The densities of states and optical conductivity clearly show the occurence of metal-insulating transition (MIT) at U$_{c}$, U$_{c}$=18.2, 16.8, 6.12 and 5.85 for J=0, 0.01U, U/4 and U/3, respectively. The distinct continuities of double occupation of electrons, local square moments and local susceptibility of the charge, the spin and the orbital at J > 0 suggest that the MIT is the first-order; however at J=0, the MIT is the second-order in the half-filling two-orbital Hubbard model on triangular lattices. We attribute the first-order nature of the MIT to the low symmetry of the systems with finite Hund's coupling J.