PERSISTENT CURRENT IN DISORDERED AHARONOV-BOHM RINGS WITH INTERACTINGELECTRONS

The role of repulsive on-site and nearest-neighbor Coulomb interaction s in disordered half-filled Aharanov-Bohm rings is studied by world-li ne quantum Monte Carlo simulations. The diverse dependence of the equi librium persistent current on the couplings is found to relate systema tically to the magnetic phase of the model: the maximum charge stiffne ss (or the persistent current) coexists with the phase-transition line between the dominant charge-density-wave state and the dominant spin- density-wave state. The stiffness vanishes with an increasing departur e from the transition line. Thus in the disordered rings the Coulomb i nteractions can enhance the charge stiffness over the noninteracting l imit in such away as to drive the system toward the phase-transition r egime.