Supercurrent flow in clean SNS junctions

Abstract

We use a multiple-scattering Green's function formalism to study the supercurrent in a SNS junction. Our results show that the supercurrent increases in steps as the transverse width increases. The abrupt increase in supercurrent occurs just above a critical transverse width in which a new transverse mode begins to contribute. It is also at this transverse width that the exact results and the ones calculated using the Andreev approximation begin to differ, marked by the appearance of oscillations in the former. It is also found that for junction lengths much larger than the BCS coherence length, the Andreev approximation and the exact treatment give the same results.