Effect of superconducting fluctuations on nuclear relaxation in zero-dimensional superconductors

The study of the effects of fluctuations on nuclear spin relaxation in samples containing grains, in which all dimensions are much smaller than the coherence length (zero-dimensional superconductors) is described. Nuclear spin-lattice relaxation provides a suitable local probe into the fluctuations of the order parameter in small superconducting grains. It is believed that the described calculation of relaxation rate which takes into account the nonlinear effects of fluctuations gives a satisfactory explanation of the data on zero-dimensional superconductors in which level quantization effects are negligible. The critical increase of relaxation rate predicted by the perturbation theory is not seen experimentally, because the nonlinear fluctuation effects renormalize the relaxation rate over a wide region of temperatures around Tsub(c). (Auth.)