VORTEX STRUCTURE AND RESISTIVE TRANSITIONS IN HIGH-T-C SUPERCONDUCTORS

The nature of the resistive transition for a current applied parallel to the magnetic field in high-T-c materials is investigated by numeric al simulation on the three-dimensional Josephson junction array model. Using finite-size scaling it is shown that for samples with disorder the temperature T-p of the c-axis resistivity transition corresponds t o a percolation phase transition of vortex lines perpendicularly to th e applied field. The value of T-p is higher than the temperature of th e resistive transition for j perpendicular to H, but decreases with th e thickness of the sample and with anisotropy. We predict that critica l behavior around T-p should reflect in experimentally accessible quan tities, as the I-V curves.