Screening of persistent currents in mesoscopic metal rings

The effect of the Coulomb-interaction on persistent currents in disordered mesoscopic metal rings threaded by a magnetic flux φ is studied numerically. We use the simplest form of self-consistent Hartree theory, where the spatial variations of the self-consistent Hartree potential are ignored. In this approximation the self-consistent Hartree energies are simply obtained by diagonalizing the non-interacting system via the Lanczos method and then calculating the (disorderdependent) particle number on the ring self-consistently. In the diffusive regime we find that the variance of the total particle number is strongly reduced, in agreement with the prediction of the random-phase approximation. On the other hand, the variance of the number of energy levels in a small interval below the Fermi energy is not affected by the Coulomb interaction. We argue that this implies that the experimentally observed enhancement of the persistent current is due to long-range Coulomb interactions.