Transition to the Normal State Induced by High Current Densities in High-Tc Superconductor Microbridges Under Applied Magnetic Fields

We report some of our experimental results about the transition to the normal state of high-temperature superconductors subjected to high current densities and, simultaneously, under external magnetic fields up to 1 T. Our data analysis, which is based on a recently published instability model, show that the quenching may be explained in terms of thermal instabilities due to self-heating favored by the nonlinear nature of the current–voltage characteristics of high- $T_{c}$ superconductors (HTS). In fact, we predict the density current $J^{\ast}$ at which the samples quench, i.e., jump abrupt to the normal state, with an accuracy around 1%. Beyond its interest from a fundamental point of view, this thermal model opens a practical way to estimate the quenching point thus avoiding the damaging or even burning up of devices in high power applications of HTS.