Proximity Effect of Superconducting Superimposed Films

This is the authors' abstract. We don't add key points for this paper.

The proximity effects of superimposed films were examined by the electron tunneling on the side of the superconductor backed with a normal metal. Gapless superconductivity was observed in the Ag-Sn and Fe-Sn systems directly from the current vs. voltage curves and also in the Pb-Ag and Pb-Fe systems from the dynamic resistance vs. voltage curves. A magnetic metal such as iron has a larger effect on the energy gap and the density of states than a normal metal such as silver. The density of states taken from the dynamic resistance vs. voltage curves was analyzed simply by replacing the collision rate in the theory of Skalski et al. for the superconductor containing paramagnetic impurities by the pair breaking parameter in the Fulde-Maki theory for a superimposed film. The agreement with the theory was good in the non-magnetic normal-super system, but was rather poor in the magnetic normal-super system.