Quantum current magnification in a multichannel mesoscopic ring

Abstract

We have studied the current magnification effect in a multichannel open mesoscopic ring. We show that the current magnification effect is robust even in the presence of several propagating modes despite mode mixing and cancellation effects. The magnitude of circulating currents in the multichannel regime can be much larger than that in a single channel case. Impurities can enhance or degrade the current magnification effect depending sensitively on the system parameters. Circulating currents are mostly associated with Fano resonances in the total transport current. We further show that system-lead coupling qualitatively changes the current magnification effect.