OBSERVATION OF THE COHERENCE PEAK OF H-1-NMR RELAXATION RATE IN THE SUPERCONDUCTING STATE OF (MDT-TTF)(2)AUI2

We have investigated the superconductivity in the organic conductor, (MDT-TTF)(2)Aul(2) (T-c = 4.1 K) from the temperature dependence of H-1 nuclear relaxation rate, 1/T-1, measured by the field cycling method. The nuclear relaxation above 3 K is well characterized by a single relaxation time for nearly two decades. In the normal state, the standard Korringa relation holds. 1/T-1, just below T-c showed a clear enhancement, followed by a falling-off at lower temperatures. This behavior is just as predicted in the BCS theory (coherence peak) and implies that this material is a conventional superconductor with an isotropic gap. The decay of the nuclear magnetization below 3 K appeared non-sinle exponential. This is explained as the effect of trapped vortices.