LARGE DYNAMICAL FLUCTUATIONS IN THE MICROWAVE CONDUCTIVITY OF YBA2CU3O7-DELTA ABOVE T-C

We report a systematic investigation of dynamical fluctuation effects in the frequency-dependent microwave conductivity (45 MHz-45 GHz) of Y Ba2Cu3O7-delta thin films for T greater than or similar to T-c. Our me asurements directly yield a dynamical critical exponent z in the range 2.3-3.0, and the fluctuation lifetime tau(fl), which diverges more qu ickly than Gaussian theory predicts as the temperature approaches T-c from above, independent of sample quality. In addition, both the tempe rature and the frequency dependence of the fluctuation conductivity si gma(fl) exhibit scaling behavior for temperatures 1-2 K above T-c, and can be collapsed onto the same universal curve.