SUPERCONDUCTING PHASE OF YBA2CU3O7-DELTA FILMS IN HIGH MAGNETIC-FIELDS - VORTEX-GLASS OR BOSE GLASS

Nonlinear current-voltage (I-V) curves are measured in laser-ablated Y Ba2Cu3O7-delta films deposited onto SrTiO3. The measurements are perfo rmed near the glass phase transition in a magnetic field of 5 T at var ious angles from the c axis. From a critical scaling analysis, the ang ular dependencies of the glass transition temperature and the critical glass exponents are extracted. At small angles, these results disting uish between a vortex glass, caused by random pointlike disorder, and a Bose glass, caused by linelike disorder. The results can be understo od in terms of the vortex-glass model only. No evidence is found for t he existence of a Bose-glass phase.