Effects of Orbital Degeneracy and Electron Correlation on Charge Dynamics in Perovskite Manganese Oxides

TL;DR

This study explores how orbital degeneracy and electron interactions influence charge behavior in perovskite manganese oxides, revealing incoherent charge dynamics and precursor signs of charge ordering near the Mott insulating phase.

Contribution

It introduces a double-exchange model incorporating orbital degeneracy and Coulomb interactions, providing new insights into charge dynamics and correlations in manganite oxides.

Findings

Optical conductivity shows a broad, incoherent structure with suppressed Drude weight.

Anomalous charge correlation at quarter filling indicates precursor to charge ordering.

Results qualitatively match experimental observations.

Abstract

Taking the orbital degeneracy of $e_g$ conduction bands and the Coulomb interaction into account in a double-exchange model, we investigate charge dynamics of perovskite Mn oxides by the Lancz$\ddot{\rm o}$s diagonalization method. In the metallic phase near the Mott insulator, it is found that the optical conductivity for a spin-polarized two-dimensional system exhibits a weight transfer to a broad and incoherent structure within the lower-Hubbard band together with a suppressed Drude weight. It reproduces qualitative feature of the experimental results. As an orbital effect, we find that an anomalous charge correlation at quarter filling suppresses the coherent charge dynamics and signals precursor to the charge ordering.