Effects of interorbital hopping on orbital fluctuations and metal-insulator transitions: Extended linearized dynamical mean-field theory

TL;DR

This study investigates how interorbital hopping influences orbital fluctuations and the metal-insulator transition in a two-orbital Hubbard model, revealing its significant role in orbital ordering and phase transitions.

Contribution

It introduces an extended linearized dynamical mean-field theory approach to analyze the impact of interorbital hopping on orbital fluctuations and MITs in the two-orbital Hubbard model.

Findings

Interorbital hopping increases the critical Hund's coupling for MIT at half-filling.

Without interorbital hopping, MIT occurs at quarter filling with decreasing J.

Increasing interorbital hopping induces a transition from metal to insulator and enhances orbital order.

Abstract

We study the effects of interorbital hopping on orbital fluctuations and Mott-Hubbard metal-insulator transition (MIT) in the two-orbital Hubbard model within the extended linearized dynamical mean-field theory. By mapping the model onto an effective model with different bandwidths through the canonical transformation, we find that at half-filling, the increases of the interorbital Coulomb interaction $U^{\prime}$ and the Hund's coupling $J$ drive the MIT, and the critical $J_{c}$ for MIT increases with the lift of the inter-orbital hopping integral $t_{ab}$. Meanwhile at quarter filling and in the strong correlation regime, the system without $t_{ab}$ exhibits MIT with the decreasing of $J$, and favors the orbital liquid ground state. However, the system transits from metal to insulator with the increasing of t$_{ab}$, accompanied with the rising of the orbital order parameter. These results show the important role of the interorbital hopping in the orbital fluctuation and orbital ordering.