FLUX-FLOW CONDUCTIVITY IN HIGH-T(C) SUPERCONDUCTORS

Using an early theory by Houghton and Maki based on the BCS model, which assumes a temperature-independent relaxation time tau, we compute the flux-flow magnetoresistivity rho(s)(T, H) of layered superconductors near H(c2) in the clean limit. Then we use our results to analyse the magnetoresistivity curves of single-crystal YBaCuO. Extending the validity of the calculation to a temperature-dependent tau, we find that for constant tau, or for relaxation times obtained from experiments, the theory reproduces qualitatively the saturation-like behaviour of the observed magnetoresistance, and also the broadening of the resistive transition, as well as the changes in the slope d(rhos)(T)/dT with field. However, quantitative agreement with experiments is not achieved. This allows an estimate to be made of the contribution of the thermal vortex line fluctuations to the total dissipation; we find the former to be about 10% of the latter.