Fluctuation Effects on the Superconducting Transition of Tin Whisker Crystals

We report the results of measurements of the resistive transitions of clean one-dimensional superconductors (pure tin whiskers) at currents of {~} 10^-7 A. Comparison with the McCumber-Halperin theory, including consideration of the current-dependent terms necessary at these current levels, yields good agreement with no adjustment of the attempt frequency. We conjecture, however, that precise conclusions concerning the magnitude of the attempt frequency cannot yet be drawn. Rather, we present arguments which suggest that a meaningful fit to the data in the top portion of the transition must await an improved theory, and that adjustments of the attempt frequency such as those used by Lukens, Warburton, and Webb (in fitting lower-current data) may not be meaningful.