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 YBa2Cu3O7-delta thin films for T greater than or similar to T-c. Our measurements directly yield a dynamical critical exponent z in the range 2.3-3.0, and the fluctuation lifetime tau(fl), which diverges more quickly than Gaussian theory predicts as the temperature approaches T-c from above, independent of sample quality. In addition, both the temperature and the frequency dependence of the fluctuation conductivity sigma(fl) exhibit scaling behavior for temperatures 1-2 K above T-c, and can be collapsed onto the same universal curve.