New Measurements of the Transition to the Normal State Induced by High Current Densities in High-Tc Superconductor Microbridges under Thermal Smallness Conditions

We address here the superconductivity quenching under an external magnetic field of amplitudes up to 1 T and in the so-called "thermal smallness" condition, when the microbridge width becomes smaller than the thermal diffusion length of both the own superconductor and its refrigerant (the substrate, in the case of thin films), which breaks their thermal dimensional scaling. Our results further support that when the current perturbations have characteristic times in the millisecond range the quenching is due to thermal instabilities associated with regular (nonsingular) flux-flow, and they also suggest how to optimize the refrigeration of practical superconductors.