Physical mechanism for a kinetic energy driven zero-bias anomaly in the Anderson-Hubbard model

TL;DR

This paper explains the zero-bias anomaly in the Anderson-Hubbard model as a kinetic energy effect arising from the mixing of Hubbard orbitals, challenging previous explanations based solely on disorder or interactions.

Contribution

It introduces a new physical mechanism linking the zero-bias anomaly to kinetic energy and orbital mixing in disordered, strongly correlated systems.

Findings

The zero-bias anomaly energy scale is proportional to hopping t.

An ensemble of two-site systems reproduces the anomaly features.

Orbital mixing explains the anomaly in strongly correlated disordered systems.

Abstract

The combined effects of strong disorder, strong correlations and hopping in the Anderson-Hubbard model have been shown to produce a zero bias anomaly which has an energy scale proportional to the hopping and minimal dependence on interaction strength, disorder strength and doping. Disorder-induced suppression of the density of states for a purely local interaction is inconsistent with both the Efros-Shklovskii Coulomb gap and the Altshuler-Aronov anomaly, and moreover the energy scale of this anomaly is inconsistent with the standard energy scales of both weak and strong coupling pictures. We demonstrate that a density of states anomaly with similar features arises in an ensemble of two-site systems, and we argue that the energy scale t emerges in strongly correlated systems with disorder due to the mixing of lower and upper Hubbard orbitals on neighboring sites.