CURRENT MAGNIFICATION AND CIRCULATING CURRENTS IN MESOSCOPIC RINGS

We show that several novel effects related to persistent currents can arise in open systems, which have no analogue in closed or isolated sy stems. We have considered a system of a metallic ring coupled to two e lectron reservoirs. We show that in the presence of a transport curren t, persistent currents can flow in a ring even in the absence of magne tic field. This is related to the current magnification effect in the ring. In the presence of a magnetic field we show that the amplitude o f persistent currents is sensitive to the direction of current flow fr om one reservoir to another. Finally, we briefly discuss the persisten t currents arising due to two nonclassical effects namely, Aharonov-Bo hm effect and quantum tunneling.