Field and temperature dependencies of the current-induced dissipation in an epitaxial YBCO thin films

Abstract

The temperature and field dependencies of isothermal current–voltage curve of an epitaxial YBa 2Cu 3O 7− δ thin film have been measured. The current-induced dissipation shows two crossovers: one is from independent on transport current to dependent on one, corresponding to the transition from free flow to thermally activated flux flow, and another is from upward curvature on current to downward one, corresponding to the transition from pinned vortex liquid state to vortex solid state. Compared with the R– T measurement, we find that the transition from independent on the transport current to dependent on one is close to the melting transition of vortex lattice. The temperature dependence of the effective pinning energy has been discussed.