Frequency dependence of the skin depth in superconducting tin

Abstract

The first measurements of the frequency dependence of the real part of the superconducting skin depth δr(v, t), in polycrystalline tin films, are reported using a new technique of measurement. The technique is similar to the usual cavity technique, except that the cavity in question is a rectangular SnSingle Bond signSnOxSingle Bond signSn Josephson tunnel junction. The cavity is self-excited via the ac Josephson effect; the resonant frequencies of the cavity are measured from which δr(v, t) is deduced. The measurements extend from 0≤v≤220 GHz and 0.5≤t≤0.952. The results are compared with Miller's calculations of δr for Sn, which are based on the Mattis-Bardeen theory and are found to be in agreement for t≤0.800. Above this temperature only qualitative agreement exists because the assumptions under which the calculations were made are here only partly satisfied. © 1969 The American Institute of Physics.