Enhancement of persistent current in mesoscopic rings and cylinders: shortest and nextpossible shortest higher-order hopping

Abstract

We present a detailed study of persistent current and low-field magnetic susceptibility insingle isolated normal metal mesoscopic rings and cylinders in the tight-binding model withhigher-order hopping integral in the Hamiltonian. Our exact calculations show that order ofmagnitude enhancement of persistent current takes place even in the presenceof disorder if we include the higher-order hopping integral in the Hamiltonian.In strictly one-channel mesoscopic rings the sign of the low-field currents canbe predicted exactly even in the presence of impurity. We observe that perfectrings with both odd and even numbers of electrons support only diamagneticcurrents. On the other hand in the disordered rings, irrespective of realization ofthe disordered configurations of the ring, we always get diamagnetic currentswith odd numbers of electrons and paramagnetic currents with even numbersof electrons. In mesoscopic cylinders the sign of the low-field currents cannotbe predicted exactly since it strongly depends on the total number of electrons,Ne, and also on the disordered configurations of the system. From the variation of persistentcurrent amplitude with system size for constant electron density, we conclude that theenhancement of persistent current due to additional higher-order hopping integrals isvisible only in the mesoscopic regime.