INFLUENCE OF A NONUNIFORM CURRENT-DENSITY PROFILE ON QUASI-PARTICLE EXCITATIONS AND THERMALLY ACTIVATED FLUX-CREEP IN YBA2CU3O7-DELTA

The transport current density, flowing radially from the center of a s uperconducting disk to its perimeter, in a so-called Corbino geometry, results in a double action on the vortex motion when the applied magn etic field is perpendicular to the disk's plane. First, the depinned v ortices are set into a nearly circular motion in the plane of the disk . Second, the non-uniform current density profile activates the intrin sic weak links, resulting in a non negligible proximity dominated quas iparticle contribution. In turn, these intrinsic junctions impede the circular motion of vortices giving rise to a proximity influenced ther mally activated flux creep. This provides a simple technique to deconv olute the flux motion and the quasiparticle induced components of the total dissipative resistivity broadening below T-c. The case for a YBa CuO disk is hereby examined and measured in this context. It is shown that such a deconvolution can be made and theoretical laws for the fie ld dependences are also obtained and confirm the data. Furthermore, th e paraconductivity region just above T-c(B) appears to be dominated by the macroscopic fluctuations accompanying the vortex core motion.