High Frequency Surface Resistivity of Tin in the Normal and Superconducting States

Measurements have been made at a frequency of 9400 megacycles per second of the unloaded $Q$ of a tin cavity from 74.9°K down to 1.26°K. From the value of the unloaded $Q$ and a knowledge of the geometry of the cavity, the high frequency surface resistivity of white tin has been calculated as a function of temperature in both the normal and the superconducting states. In the normal state at low temperatures, the surface resistivity becomes independent of the d.c. resistivity in agreement with workers at other frequencies. In this region the experimental data are compared with the theoretical curves of Sondheimer and Reuter and a value obtained for the number of conduction electrons per atom. Below the superconducting transition temperature the resistivity drops rapidly with temperature, approaching asymptotically a value of 1.9 percent of the value of the resistance at the transition temperature. The results are compared with the data of Pippard and the probable dependence of residual resistance on the method of preparing the tin samples is discussed.