Weakly coupled grain model of high-frequency losses in high <i>T</i> <i>c</i> superconducting thin films

Abstract

We propose a model of Josephson coupling between grains to explain the millimeter-wave surface impedance of oriented, polycrystalline thin films of high Tc superconductors. An effective junction IcR product and effective grain size are calculated based on recent measurements of the surface impedance. We suggest a criterion on film quality for the observation of losses intrinsic in the superconductor. The effects of crystalline orientation on surface impedance are considered.