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

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