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) microbri dge 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 re sults have been reported, in addition to the static characteristics of the vortex system (de limit). In consistency with the concept of a co rrelation 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 a n experimental uncertainty of 1 K. In conflict to previous reports, th e real and imaginary components of the ac-linear voltage at T=T-g(B) w ere found to follow the same power law V-i proportional to V-o proport ional 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 t ime exceeds 10 mu s.