Effect of thermodynamic fluctuations on the shape and width of the resistive transition in three-dimensional amorphous superconducting alloys

Abstract

Measurements of the fluctuation conductivity above $T_c$ have been made for several bulk amorphous superconducting alloys. The results are compared to existing theories for fluctuation conductivity in three-dimensional superconductors. Agreement with theory is obtained very near $T_c$, but significant deviations from the predictions of the theory are found for higher temperatures. This is attributed to a breakdown of the Ginzburg-Landau approach. The observed temperature dependence of the fluctuation conductivity was similar in all samples studied and suggests a universal dependence on temperature for bulk amorphous superconductors. The effect of statistical variations in alloy composition (occurring on the scale of the superconducting coherence length $\xi$ on the width of the superconducting transition widths was observed.