Persistent currents in interacting electronic systems

TL;DR

This paper investigates persistent currents in disordered mesoscopic rings with electron interactions, revealing the crucial influence of spin degrees of freedom and charge density fluctuations on current behavior.

Contribution

It compares 1D and 2D models, showing the importance of spin in accurately modeling persistent currents beyond simple approximations.

Findings

1D models underestimate current magnitude.

Second harmonic suppressed in spinless models, enhanced in Hubbard models.

Spin degrees of freedom significantly affect current properties.

Abstract

Persistent currents in disordered mesoscopic rings threaded by a magnetic flux are calculated using exact diagonalization methods in the one-dimensional (1D) case and self-consistent Hartree-Fock treatments for two dimensional (2D) systems. For multichannel systems, a comparative study between models of spinless or spinfull (Hubbard) fermions has been done. First, it is shown that a purely one-dimensional model can not reproduce the correct order of magnitude of the observed currents. For 2D systems, going beyond first order pertubative calculations, we show that the second harmonic of the current is {\it strongly suppressed} in the case of spinless fermion models but {\it significantly enhanced} for the Hubbard model. This reduction (resp. increase) of the second harmonic is related to a strong increase (resp. reduction) of the spacial charge density fluctuations. Our work underlines the important role of the spin degrees of freedom in the persistent currents.