rf surface impedance of a two-band superconductor

Abstract

In this paper, we extend the Mattis-Bardeen theory to obtain the surface impedance of a two-band superconductor, and apply it to magnesium diboride (MgB_{2}) for radiofrequency (rf) superconductivity applications. The numerical results for MgB_{2} are in good agreement with the previously published experimental results. The surface impedance properties are clearly dominated by the smaller gap, significantly limiting utility in the 10-20 K regime that might otherwise have been attractive.