THE SURFACE IMPEDANCE OF HIGH T_{<font>c</font>} SUPERCONDUCTORS

Abstract

Recent experiments on the surface impedance of the high temperature superconductors are summarized. The overall temperature dependence of the penetration depth is in broad qualitative agreement with conventional pairing, but with an anomolous power law behavior observed at low temperatures. The surface resistance is orders of magnitude larger than estimates based on the Mattis-Bardeen theory. One possibility is unconventional pairing, but structural inhomogenities are the most likely explanation for the experimental results.