Enhanced Charge and Spin Currents in the One-Dimensional Disordered Mesoscopic Hubbard Ring

TL;DR

This paper investigates how disorder and interactions influence charge and spin currents in a one-dimensional mesoscopic Hubbard ring, revealing conditions under which currents are enhanced or suppressed.

Contribution

It provides a detailed analysis of charge and spin current behavior in disordered Hubbard rings, highlighting the effects of interaction strength and disorder on persistent currents.

Findings

Charge currents can be larger than free system beyond a critical disorder strength.

Spin currents are enhanced at small U in the presence of disorder.

At large U, spin currents are suppressed due to localized spins.

Abstract

We consider a one-dimensional mesoscopic Hubbard ring with and without disorder and compute charge and spin stiffness as a measure of the permanent currents. For finite disorder we identify critical disorder strength beyond which the charge currents in a system with repulsive interactions are {\em larger} than those for a free system. The spin currents in the disordered repulsive Hubbard model are enhanced only for small $U$, where the magnetic state of the system corresponds to a charge density wave pinned to the impurities. For large $U$, the state of the system corresponds to localized isolated spins and the spin currents are found to be suppressed. For the attractive Hubbard model we find that the charge currents are always suppressed compared to the free system at all length scales.