EFFECT OF SUPERCONDUCTIVITY FLUCTUATIONS ON THE NMR RELAXATION RATE OF HIGH-T(C) SUPERCONDUCTORS

The effect of superconducting order parameter fluctuations on the nuclear-spin relaxation rate, 1/T1, is studied for clean two-dimensional systems by calculating the three Maki-Thomson-type diagrams which represent the lowest-order fluctuation contributions to the transverse susceptibility. For Gaussian fluctuations and for temperatures near the mean field transition temperature, T(c0), we employ a weak-coupling theory in which the pair-fluctuation propagator can also include pair-breaking effects. We also go beyond the Gaussian theory and take into account the interactions between Cooper-pair fluctuations corresponding to the fourth-order Ginzburg-Landau fluctuation terms. We compare our results with previous results in the dirty limit and in 3D. We obtain a pronounced peak in 1/T1 at T(c) and briefly discuss possible reasons why this peak is not observed.