Exact and mean-field analysis of the role of Hubbard interactions on flux driven circular current in a quantum ring

TL;DR

This paper analyzes how Hubbard interactions, disorder, and electron filling influence persistent circular current in quantum rings using exact diagonalization and mean-field methods.

Contribution

It introduces a linear table formalism for constructing the many-body Hamiltonian and systematically studies the effects of various interactions and disorder on current behavior.

Findings

Current decreases monotonically with on-site repulsion in ordered rings.

Extended interactions have filling-dependent effects on current, suppressing or enhancing it.

Disorder can significantly enhance current at low fillings with increased extended interaction.

Abstract

We investigate circular current in both ordered and disordered Hubbard quantum rings threaded by magnetic flux, employing exact diagonalization and the Hartree-Fock mean-field approach within the tight-binding framework. The influence of on-site and extended Hubbard interactions, disorder, and electron filling on the persistent current is systematically analyzed. To construct the full many-body Hamiltonian, we introduce a linear table formalism, which, to our knowledge, has been rarely used in this context. In ordered rings, the current decreases monotonically with increasing on-site repulsion, while the impact of the extended interaction depends strongly on the filling factor. At low filling, stronger extended interaction suppresses the current, whereas near half-filling, it enhances the current up to a critical ratio, half of the on-site strength, before reducing it. Disorder significantly modifies these behaviors, notably enhancing the current at less than quarter-filling with increasing extended interaction. The localization properties of eigenstates, examined via the inverse participation ratio, further support the crucial roles of filling and the interplay between on-site and extended interactions in governing persistent current.