Aharonov-Bohm oscillations in the conductance of a disordered mesoscopic ring with superconducting inclusions

The conductance of a normal metal ring with two transverse superconducting "mirrors", is calculated as a function of the magnetic flux. The calculatio n shows an hc/e periodic oscillation for a clean ring. In a disordered ring , simulated by taking an ensemble-average over the length configuration, on the other hand, the frequency of the oscillation becomes doubled giving a period of hc/2e. With superconducting "barriers". with which is modeled the effect of the particle-hole coherence prevailing on the ring due to the An dreev reflections from the "mirrors", the frequency is found to double agai n resulting in a period of hc/4e. (C) 1998 Published by Elsevier Science Lt d. All rights reserved.