FLUX-FLOW AND PHASE-SLIP DISSIPATION IN CRYSTALLINE BI2SR2CACU2O8+DELTA AND YBA2CU3O7-DELTA

The microwave-dissipation experiments of Zuo et al. [Phys. Rev. B 41, 6600 (1990)] on YBa2Co3O7-delta and Bi2Sr2CaCu2O8 + delta crystals have been reanalyzed in terms of flux-flow and phase-slip resistivities. In addition to small flux-flow signals, a thermally activated field-dependent signal, which arises from phase slip in a network of weak links, is described. Phase-slip resistivity is the dominant loss mechanism near T(c). The resulting four-parameter model for the field-dependent surface resistance R(s) has been used to compute dR(s)/dH, which their experiment measures. The measurements reviewed here were carried out over the temperature range of 61-82 K, with the applied magnetic field varying to a maximum of 0.2 T applied parallel to the c axis, and with the rf current in the c plane. The data have been successfully fit yielding estimates of the phase-slip barrier energy A, the critical field H(c2), the residual surface resistance, and an effective field H0, which describes the width of the transition. The primary consequence of the analysis is that the model for high-temperature-superconductivity resistivity given by Tinkham is supported, with the inclusion of a modified expression for flux flow.