LORENTZ-FORCE-INDEPENDENT DISSIPATION IN HIGH-TEMPERATURE SUPERCONDUCTORS

The evolution of resistivity in the mixed state of high-T(c) superconductors has been a source of debate in the fundamental problem of whether or not energy dissipation originates from the Lorentz-force-driven flux motion. The conventional flux-creep and flux-flow models are essentially based on this mechanism and have frequently been used to explain the broad resistive transition in magnetic fields in high-T(c) superconductors. However, recent intensive experimental studies of high-quality single crystals, such as (La1-xSrx)2CuO4, YBa2Cu3O7-delta, Bi2Sr2CaCu2O8+delta etc, have revealed clear evidence that excludes the contribution of the effect of flux motion to the resistivity broadening, indicating that the conventional flux-motion mechanism does not play a major role in dissipation in high-T(c) superconductors. Instead, mechanisms that take into account the superconducting fluctuation effect in the superconducting order parameter have recently been proposed and have successfully been applied to analyse experimental results. Possible similarities between the fundamental concepts of superconducting fluctuation models and the Kosterlitz-Thouless transition have also been discussed.