Two-particle excitations under coexisting electron interaction and disorder

TL;DR

This paper investigates how disorder and electron interactions influence the optical absorption and localization in a 3D Hubbard model, revealing that electron-hole interactions significantly alter the system's response and critical disorder thresholds.

Contribution

It introduces a comprehensive analysis combining disorder, electron-electron, and electron-hole interactions using advanced many-body techniques, highlighting their combined effects on optical properties and localization.

Findings

Disorder reduces absorption and conductivity, leading to electron localization.

Electron-hole interactions significantly modify oscillator strength and critical disorder.

Quantum corrections from electron-hole interactions lower the disorder threshold for localization.

Abstract

We study the combined impact of random disorder and electron-electron, and electron-hole interactions on the absorption spectra of a three-dimensional Hubbard Hamiltonian. We determine the single-particle Green's function within the typical medium dynamical cluster approximation. We solve the Bethe-Salpeter equation (BSE) to obtain the dynamical conductivity. Our results show that increasing disorder strength at a given interaction strength leads to decreased absorption with the dynamical conductivity, systematically going to zero at all frequencies, a fingerprint of a correlation-mediated electron localization. Surprisingly, our data reveal that taking into account the effects of electron-hole interactions through the BSE significantly changes the oscillator strength with a concomitant reduction in the critical disorder strengths $W_c^U$. We attribute this behavior to enhanced quantum correction induced by electron-hole interactions.