CURRENT-ACTIVATED RESIDUAL SURFACE-RESISTANCE IN HIGH-TEMPERATURE SUPERCONDUCTORS

A prominent and unusual feature of the microwave surface resistance of high temperature superconductors is a comparatively large "residual" resistance observed from a few degrees below the transition temperature, to the lowest temperatures. This resistance, which varies slowly with temperature, is also observed to vary with the rf field amplitude, sample quality, and frequency. Using a classical treatment for the rf field, we show that a surface resistance approximately mohms arises from current-activated phase-slip resistivity. At low temperatures, this contribution to the surface resistance varies approximately as omega-H(rf)/J(c0), where omega is the angular frequency, H(rf) is the rf field amplitude, and J(c0) is the inter-granular critical current.