Depairing critical currents and self-magnetic field effects in submicron YBa2Cu3O7-delta microbridges and bicrystal junctions

We report on depairing critical currents in submicron YBa2Cu3O7-delta microbridges. A small-angle bicrystal grain boundary junction is used as a tool to study the entrance of vortices induced by a transport current and their influence on the I-V curves. The interplay between the depairing and the vortex motion determines a crossover in the temperature dependence of the critical current. The high entrance field of vortices in very narrow superconducting channels creates the possibility of carrying a critical current close to the depairing limit determined by the S-S-'-S nature of the small-angle grain boundary junction. (C) 2004 American Institute of Physics.