Non-universal glass scaling behavior in transport properties of YBa₂Cu₃O_y films with columnar defects

Vortex phase diagrams have been studied on heavy-ion irradiated YBa₂Cu₃O_y films by the measurements of current-voltage (I-V) characteristics, resistance R and critical current density J_c as a function of magnetic field B parallel to the columnar defects. In the scaling analyses of the I-V data, we find the non-universal nature of the glass transition. The dynamic critical exponent z, which is almost constant at high fields, shows an anomalous peak and the glass transition line T_g(B) reveals an upturn behavior at B ∼ B_φ/3 with B_φ the matching field, where we also observe step-like behavior both in R(B) and J_c(B) curves. These results indicate the existence of a temperature-independent boundary in the B-T plane at which the dissipation mechanism changes.