Large Dynamical Fluctuations in the Microwave Conductivity of YBa2Cu3O7- delta above Tc.

We report a systematic investigation of dynamical fluctuation effects in the frequency-dependent microwave conductivity (45 MHz–45 GHz) of YBa2Cu3O72d thin films for T * Tc. Our measurements directly yield a dynamical critical exponent z in the range 2.3–3.0, and the fluctuation lifetime tfl, which diverges more quickly than Gaussian theory predicts as the temperature approaches Tc from above, independent of sample quality. In addition, both the temperature and the frequency dependence of the fluctuation conductivity sfl exhibit scaling behavior for temperatures 1–2 K above Tc, and can be collapsed onto the same universal curve. [S0031-9007(96)01664-X]