Threshold Field Properties of Some Superconductors

Abstract

Some refined measurements of the critical field curves for tin, thallium, indium, and mercury have been completed and the results compared with the specific predictions of the Gorter-Casimir and the Koppe versions of the two-fluid model of superconductivity. Neither version is completely adequate, although each has points in its favor. The Koppe prediction of a universal critical field curve for all superconductors is not verified. The Gorter-Casimir α model has greater flexibility than the Koppe model, and although it is capable of giving a fair description of the critical field data, it is in some respects also inconsistent with the data. The isotope effect in thallium has been observed and is consistent with the half-power law.