Orbital Insulators and Orbital Order-disorder Induced Metal-Insulator Transition in Transition-Metal Oxides

TL;DR

This paper investigates how orbital order influences the metal-insulator transition in transition-metal oxides, revealing the dependence of the insulating gap on orbital order and the effects of thermal fluctuations.

Contribution

It introduces a cluster self-consistent field approach to study orbital effects in strongly correlated oxides, highlighting the orbital order-disorder transition's impact on electronic properties.

Findings

Insulating gap depends on orbital order parameter.

Thermal fluctuations induce orbital order-disorder transition.

Orbital polarization shows unusual temperature dependence.

Abstract

The role of orbital ordering on metal-insulator transition of transition-metal oxides is investigated by the cluster self-consistent field approach in the strong correlation regime. A clear dependence of the insulating gap on the orbital order parameter is found in the single-particle excitation spectra. The thermal fluctuation drives the orbital order-disorder transition, diminishes the gap and leads to the metal-insulator transition. The interplay between spins and orbits results in unusual temperature dependence of the orbital polarization in the orbital insulator, which can be seen in the resonant x-ray scattering intensity.