PERSISTENT CURRENTS IN INTERACTING SYSTEMS - ROLE OF THE SPIN

Persistent currents flowing through disordered mesoscopic rings thread ed by a magnetic flux are investigated. Models of fermions with on-sit e interactions (Hubbard model) or models of spinless fermions with nea rest neighbor interactions are considered on 2D cylinders with twisted boundary conditions in one direction to account for a magnetic flux. Self-consistent Hartree-Fock methods are used to treat the electron-el ectron interaction beyond first order. We show that the second harmoni c of the current (which is relevant in the diffusive regime) is strong ly suppressed by the interaction in the case of spinless fermions whil e it is significantly enhanced in the Hubbard model. Our data also str ongly suggest that the reduction (increase) of this harmonic is relate d to a strong increase (reduction) of the spatial fluctuations of the charge density.