Nondiverging vortex pinning barriers at low current densities across the putative elastic vortex-glass - Vortex-liquid transition in YBa₂Cu₃O_7-δ films

A detailed analysis of the electric field-current density (E-J) characteristics of YBa₂Cu₃O_7-δ films across the putative thermally induced elastic vortex-glass - vortex-liquid transition predicted by the E(J) curve scaling reveals that the expected increase of the collective pinning barriers with decreasing J is cut off in the low-J region, signaling a dissipation process which involves the plastic deformation of the vortex system. The temperature and magnetic field dependence of the pinning barriers at low J does not change across the scaling-predicted glass transition line. For the investigated magnetic field range (0.5-7 T), over a relatively large temperature interval, in YBa₂Cu₃O_7-δ films there appears a continuous crossover in a pinned plastic vortex assembly, rather than a thermally induced elastic vortex-glass - vortex-liquid transition.