Fluctuations of the Order Parameter in Small Superconducting Samples

Abstract

We study the effect of the time-dependent fluctuations of the order parameter in superconducting samples in which the dimensions are smaller than the coherence length. We find that within the mean field theory, the static properties (specific heat, spin susceptibility), as well as the transport properties, nuclear-spin relaxation time, and the tunneling density of states, diverge as $T$ approaches $T_c$. Therefore, the fluctuation corrections are much more important in those "zero-dimensional" superconductors than in the one-, two-, and three-dimensional ones. In particular, the width of the critical region is very large and increases when the size of the samples decreases. These effects should be observable if the problems of sample preparation can be solved.