Hartree-Fock study of an Anderson metal-insulator transition in the presence of Coulomb interaction: Two types of mobility edges and their multifractal scaling exponents

TL;DR

This study explores how Coulomb interactions influence the multifractal properties of eigenfunctions at the Anderson metal-insulator transition, revealing two distinct mobility edges with different scaling behaviors.

Contribution

It demonstrates the existence of two types of mobility edges influenced by Coulomb interactions and characterizes their multifractal scaling properties using Hartree-Fock approximation.

Findings

Two mobility edges identified near Fermi energy and high energy

Multifractal spectra confirm two types of scale-invariance

Distinct multifractal exponents for each mobility edge

Abstract

In summary, we investigated the role of Coulomb interactions in the nature of eigenfunction multifractality of an Anderson metal-insulator transition, based on the Hartree-Fock approximation and the Ewald summation technique. As a result, we showed that two types of mobility edges appear near the Fermi energy and at a high energy, respectively, where the low-energy mobility edge results from Coulomb interactions while the high-energy one is nothing but the mobility edge of the Anderson localization transition without electron correlations. Indeed, not only multifractal scaling exponents but also the multifractal singularity spectrum confirms the existence of two kinds of mobility edges: Their values differ from those of the Anderson metal-insulator transition and the singularity spectrum collapses into two types of curves, implying two kinds of scale-invariance, which depends on the energy scale. We speculate that this novel nature of the eigenfunction multifractality would serve as valuable information for possible instabilities near a metal-insulator transition in the presence of Coulomb interactions.