Self-heating effects on the transition to a highly dissipative state at high current density in superconducting YBa₂Cu₃O_7-δ thin films

We report current-voltage characteristics (CVC’s) and voltage against time curves at constant current on c-axis oriented YBa₂Cu₃O_7-δ superconducting thin-film microbridges. Measurements were done up to high enough current densities to trigger the quenching, i.e., an abrupt voltage jump to a highly dissipative state. Our data analyses show that, due to the nonlinear behavior of the measured CVC’s, uniform Joule heating dissipation can produce by itself quite abrupt transitions. The reduced temperature dependence of the measured quenching current density J^*∝ε^3/2, currently interpreted as a signature for intrinsic quenching mechanisms, is reproduced by our self-heating based calculations. Also, the paradoxical dependence of an increasing power at quenching with the applied magnetic field finds a natural explanation on a thermal stability criterion that explicitly takes into account the strong dependence of the sample’s dissipative power with temperature. These findings suggest that even if the origin of the quenching stands on some intrinsic mechanism, the heating effects in thin films may play a more important role than considered so far.