Effect of Coulomb repulsion and magnetic frustration on persistent currents in the Hubbard model

The interplay between Coulomb repulsion and magnetic frustration and its effect on persistent currents in the Hubbard model are studied. We consider a system of tight-binding electrons confined to a cylindrical geometry subject to a solenoid flux threading its center and a magnetic field perpendicular to the face. Were, the magnetic field introduces frustration, the Aux per plaquette in units of flux quantum, f = p/q with p and q being relative prime integer. Mean-field calculations show that the on-site Coulomb repulsion decreases the persistent current by opening a gap at the Fermi level. The suppressive role of the Coulomb interaction is influenced by the frustration, which depends on the parity of for the half-filled case. For odd q, the persistent current is suppressed by the frustration, but the opposite is true for even q; i.e., the frustration reduces the interaction effect and enhances the persistent current. [S0163-1829(99)03115-X].