Conducting Phase in the Two-Dimensional Disordered Hubbard Model

Abstract

We study the temperature-dependent conductivity $\sigma \left(T\right)$ and spin susceptibility $\chi \left(T\right)$ of the two-dimensional disordered Hubbard model. Calculations of the current-current correlation function using a quantum Monte Carlo method show that repulsion between electrons can significantly enhance the conductivity, and at low temperatures change the sign of $d\sigma /\mathrm{dT}$ 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 $\chi \left(T\right)$.