k-dependent spectrum and optical conductivity near metal-insulator transition in multi-orbital Hubbard bands

TL;DR

This paper uses dynamical mean field theory with iterative perturbation to analyze the spectrum and optical conductivity of multi-orbital Hubbard models near the metal-insulator transition, revealing the interplay of multiplet structure and electron correlations.

Contribution

It introduces a detailed DMFT-IPT approach to study spectral and optical properties in multi-orbital systems across different electron fillings.

Findings

Spectral features include multiplet effects and coherent peaks at the Fermi level.

Identification of the critical Coulomb U for metal-insulator transition.

Calculation of optical conductivity across various electron occupations.

Abstract

We apply the dynamical mean field theory (DMFT) in the iterative perturbation theory(IPT) to doubly degenerate eg bands and triply degenerate tg bands on a simple cubic lattice and calculate the spectrum and optical conductivity in arbitrary electron occupation. The spectrum simultaneously shows the effects of multiplet structure and DMFT together with the electron ionization and affinity levels of different electron occupations, coherent peaks at the Fermi energy in the metallic phase and a gap at an integer filling of electrons for sufficiently large Coulomb U. We also calculate the critical value of the Coulomb U for degenerate orbitals.