Andreev resonances in quantum ballistic transport in SNS junctions

We report the results of an investigation of the effect of the superconduct ing bound states on coherent multiple Andreev reflections in quantum SNS ju nctions. A rich resonant structure of the current, associated with the boun d states and consisting of peaks, onsets and oscillations, is found by nume rical calculations. Positions of the current structures are not given by su bharmonics of the energy gap but rather determined by the junction geometry . We present analytical classification of the resonant current structures a nd calculate their positions and amplitudes. We show that the resonant curr ent structures in three-terminal SNS interferometers can be controlled by e xternal magnetic flux. (C) 2001 Elsevier Science B.V. All rights reserved.