Soft Hubbard gaps in disordered itinerant models with short-range interaction

TL;DR

This paper investigates the emergence of unconventional soft gaps in the density of states of disordered itinerant models with short-range interactions, revealing a universal scaling behavior independent of electron filling and long-range order.

Contribution

It introduces a new type of soft gap in the Anderson-Hubbard model characterized by a specific exponential scaling form, and proposes a multi-valley energy landscape as its origin.

Findings

Existence of unconventional soft gaps with a specific energy scaling.

Scaling form of the density of states is universal across different fillings.

Proposed experimental setups to verify the theory.

Abstract

We study the Anderson-Hubbard model in the Hartree-Fock approximation and the exact diagonalization under the coexistence of short-range interaction and diagonal disorder. We show that there exist unconventional soft gaps, where the single-particle (SP) density of states (DOS) $A$ follows a scaling in energy $E$ as $A(E)\propto \exp[-(-\gamma\log |E-E_F|)^d]$ irrespective of electron filling and long-range order. Here, $d$ is the spatial dimension, $E_F$ the Fermi energy and $\gamma$ a non-universal constant. We propose a multi-valley energy landscape as their origin. Possible experiments to verify the present theory are proposed.