LOCAL PROBE OF VORTEX PINNING ENERGIES IN THE BOSE GLASS

Columnar defects provide strong pinning centers for vortices in high-T-c superconductors, increasing global critical currents. Using a magnetometer array of micron dimensions, we characterize the local held profiles in untwinned single crystals of YBa2Cu3O7-delta with equivalent columnar defect densities B-phi. We find that the critical current is large only where the internal magnetic field B<B-phi. In regions of the crystal where B>B phi, the critical current is sharply reduced. We model both local and global critical current measurements by generalizing the Bean picture to the case of irradiated high-T-c superconductors.