Temperature dependence of the maximum d.c. Josephson current in superconducting proximity junctions

Abstract We measured the temperature dependence of the maximum d.c. Josephson current I M ( T ) in Nb-Nb x O y -Al/Pb and Nb-Nb x O y -Cu/Pb junctions. We observed a different curvature of I M vs T for different normal metal thicknesses of the N/S proximity sandwich, a saturation of I M ( T ) at low temperature, a [T c (N/S)-T] 3 2 law at high temperature and a bump near the transition temperature T c ( N/S ). The behaviours are well described by numerical calculations of I M , based on the McMillan model for the proximity effect.