Conducting phase in the two-dimensional disordered Hubbard model

TL;DR

This study investigates how electron interactions and disorder influence conductivity and magnetic properties in a 2D Hubbard model, revealing a potential metallic phase and metal-insulator transition driven by temperature and interactions.

Contribution

It demonstrates that electron repulsion can induce a metallic phase in a disordered 2D Hubbard model, suggesting a possible metal-insulator transition with non-Fermi liquid behavior.

Findings

Repulsion enhances conductivity at low temperatures.

Sign change in $d\sigma/dT$ indicates a transition from insulating to conducting behavior.

Metallic phase exhibits Curie-like spin susceptibility, indicating local moments.

Abstract

We study the temperature-dependent conductivity $\sigma(T)$ and spin susceptibility $\chi(T)$ of the two-dimensional disordered Hubbard model. Calculations of the current-current correlation function using the Determinant Quantum Monte Carlo method show that repulsion between electrons can significantly enhance the conductivity, and at low temperatures change the sign of $d\sigma/dT$ from positive (insulating behavior) to negative (conducting behavior). This result suggests the possibility of a metallic phase, and consequently a metal-insulator transition,in a two-dimensional microscopic model containing both interactions and disorder. The metallic phase is a non-Fermi liquid with local moments as deduced from a Curie-like temperature dependence of $\chi(T)$.