Current-voltage characteristics in a mixed state of high Tc superconductor

Depinning properties in a random pin medium under the influence of thermal agitation have been studied by the Monte-Carlo method. It has been shown that the depinning probability is scaled on a power function in the vicinity of the depinning threshold, that is the minimum value of critical current density. The simulation results have been compared with the measurements in a Y1Ba2Cu3O7-delta thin film, then the scaling based on the statistic feature of critical current density is confirmed. The scaling is consistent with that of the well-known glass-liquid transition within the measured electric field region. A new analytical expression describing the current-voltage curves has also been derived then the origin of the extremely wide scaling regime is discussed.