Disappearance of bose-glass behavior in transport properties of YBa₂Cu₃O_y films with columnar defects

The glass transitions of the vortex system in Au-ion irradiated YBa₂Cu₃O_y films have been studied by the measurements of transport properties as a function of magnetic field B and angle Θ of B to the direction of columnar defects. At χ = 0°, we find an anomalous upturn behavior of the glass transition line B_g(T) at B ∼ B_Φ/3, where B_os is the matching field. In B > B_Φ/3, the χ dependence of glass transition temperature T_g reveals cusplike behavior with a peak at χ = 0°, which is consistent with the Bose glass theory. In B < B_Φ/3, on the other hand, T_g is almost independent of χ, suggesting the system undergoes the vortex glass transition induced by the inherent point-like defects.