The supercritical fields of metastable Type I superconductors

A precise knowledge of the superheated and supercooled transition fields of Type I superconductors is of importance to the ongoing research and development of superconducting radiation detectors, since determining whether or not the material exhibits a full degree of metastability is necessary to knowing whether the measurements are performed in metastable or intermediate state regimes. We show that, in fact, much of the information regarding device performances has been obtained from devices not fully metastable. We further examine the relationship between the supercritical fields and the Ginzburg–Landau parameter, and review the available data in tin and indium in its regard. Empirical relations are developed from which the supercritical fields can be generally determined.