Andreev resonances in quantum ballistic transport in SNS junctions

We report the results of an investigation of the effect of the superconducting bound states on coherent multiple Andreev reflections in quantum SNS junctions. A rich resonant structure of the current, associated with the bound states and consisting of peaks, onsets and oscillations, is found by numerical calculations. Positions of the current structures are not given by subharmonics of the energy gap but rather determined by the junction geometry. We present analytical classification of the resonant current structures and calculate their positions and amplitudes. We show that the resonant current structures in three-terminal SNS interferometers can be controlled by external magnetic flux. (C) 2001 Elsevier Science B.V. All rights reserved.