Abstract
Based on microscopic wave functions, we investigate the proximity effect in the superconductor(S)-normal material(N) model system, and obtain the Gor'kov's integral kernel which is exact in general cases between the clean and the dirty limit. With use of this kernel, limitations of De Gennes's theory is clarified. Our theory can be applied to the cases where the wave characters of the Cooper pair prevails, and De Gennes's theory is not valid. We also treat the case, where the chemical potential in the normal material is changed across the band edge. The decay length of the integral kernel shows a drastic change from Pippard's characteristic length to the atomic length. This character can be utilized for the design of good switching device. Further, the supercurrent in the S-N-S junction is obtained. It is theoretically shown that the good switching device can be fabricated, if the chemical potential is chosen near the band edge of the normal material, and the width of the normal material is the same order as the decay length of Cooper pair.
Published Version
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