THEORY OF SUPERCONDUCTING PROXIMITY EFFECT IN A 3-DIMENSIONAL SYSTEM IN THE CLEAN LIMIT

The superconducting proximity effect is theoretically investigated for a three-dimensional system in the clean-limit case based on a microscopic wave function. The spatial dependence of the pair potential is clarified with use of the numerical solution of the Gorkov equation for the step-function S-N model. The reduction of the pair potential at the fixed point of the superconductor side S is calculated as a measure of the degree of the proximity effect. This quantity is found to be determined by (kF/kF), which is the ratio of the Fermi wave number in the N region to that in the S region. This effect is explained by the conservation of the parallel momentum of the electron to the interface. © 1990 The American Physical Society.