Study of the geometrical resonances of superconducting tunnel junctions

Abstract
The resonant cavity structure of superconducting Sn‐Sn‐oxide‐Sn tunnel junctions has been investigated via photon‐assisted quasiparticle tunneling. We find that the temperature‐dependent losses at 35 GHz are determined by the surface resistance of the Sn films for reduced temperatures between 0.5 and 0.8. Our results are in very good agreement with the microscopic theory of Mattis and Bardeen for the surface resistance of Sn.