ENHANCEMENT OF BOSE-GLASS SUPERCONDUCTIVITY IN YBA2CUO7-DELTA

Dynamic scaling analyses of the ac conductivity measured between 1 and 190 kOe before and after heavy ion irradiation parallel to the c axis reveal continuous phase transitions to superconducting glassy vortex states. A first unambiguous evidence for the predicted Bose-glass (BG) behavior being stable up to the matching field H-phi = 40 kOe is pres ented. The critical exponents differ significantly from those obtained for H perpendicular to c and those reported recently for twin-free cr ystals, suggesting that the inherent uncorrelated disorder in thin fil ms reduces the vortex line wandering, and therefore enhances the BG tr ansition.