CORRELATION LENGTH AND TIME IN THE VORTEX-GLASS CRITICAL REGIME IN YBA2CU3O7-X FILMS

We report on the complex conductivity of a YBa2Cu3O7-x (YBCO) microbridge in the presence of magnetic field 0.5 less than or equal to B less than or equal to 6.5 T applied parallel to the c-axis. A broad range of frequences 10 less than or equal to f less than or equal to 2x10(6) Hz for the transport current passing through the bridge allows us to explore the ac dynamical response of the vortices where conflicting results have been reported, in addition to the static characteristics of the vortex system (de limit). In consistency with the concept of a correlation length and a correlation time that diverge at the transition temperature T-g(B), we demonstrate that a single value for T-g(B) can be identified in both the static and dynamical measurements, within an experimental uncertainty of 1 K. In conflict to previous reports, the real and imaginary components of the ac-linear voltage at T=T-g(B) were found to follow the same power law V-i proportional to V-o proportional to f(alpha), with alpha=0.82+/-0.05. Finally, as T-->Tg(+), the critical scaling laws break down when the diverging vortex correlation length matches the film thickness of our sample and the correlation time exceeds 10 mu s.