Quantum current magnification in a multichannel mesoscopic ring

Abstract

We have studied the current magnification effect in a multi-channel open mesoscopic ring. We show that the current magnification effect is robust even in the presence of several propagating modes inspite of 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.

Persistent current magnification in a double quantum-ring system

“…The persistent currents also have been reported in open systems. In these systems, the persistent current magnification effect have been predicted for several authors 15,16,17 .…”

“…For instance Pareek and Jayannavar 15 reported persistent current magnification in two mesoscopic rings connected to an electron reservoir, Yi et al 16 find giant persistent currents in open Aharonov-Bohm rings and Bandopadhyay et al 17 obtain persistent current magnification in multichannel mesoscopic ring.…”

A comparative study of two phenomenological models of dephasing in series and parallel resistors

“…near kL = 5.6, we now observe non-zero j c in presence of non-zero α(=0.05) though at the same points with α = 0 circulating current density was absent ( Fig.5). This clearly goes against the basic notion of dephasing -as this is enhancement of an effect (circulating current) purely attributed to phase coherence 19 . SA method is seen to be free from such discrepancies.…”

“…In the method of stochastic absorption P u = exp(−αL u ) and P d = exp(−αL d ) act as the continu- 18,19,21 . The Fano resonances accompany occurrences of circulating current in the ring.…”

“…In presence of transport current through an asymmetric ring system, depending on Fermi-energy, in one of the arms current can be larger than the transport current. Thus it is known as current magnification 18,19,21 . In such a case, to maintain current conservation, in the other arm, current flows opposite to the bias.…”