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

Using an early theory by Houghton and Maki based on the BCS model, whi ch assumes a temperature-independent relaxation time tau, we compute t he flux-flow magnetoresistivity rho(s)(T, H) of layered superconductor s near H(c2) in the clean limit. Then we use our results to analyse th e magnetoresistivity curves of single-crystal YBaCuO. Extending the va lidity 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 t he observed magnetoresistance, and also the broadening of the resistiv e transition, as well as the changes in the slope d(rhos)(T)/dT with f ield. However, quantitative agreement with experiments is not achieved . This allows an estimate to be made of the contribution of the therma l vortex line fluctuations to the total dissipation; we find the forme r to be about 10% of the latter.