Transport characteristics near the glass-liquid transition temperature before and after heavy-ion irradiation in a YBa₂Cu₃O_7-δ thin film

We investigated the influence of flux pinning on the behavior of flux lines in a c-axis oriented YBa₂Cu₃O_7-δ thin film, by analyzing the critical scaling of current-voltage charac-teristics at various temperatures under the magnetic field parallel to the c-axis before and after irradiation. In the irradiation process, splayed columnar defects were produced in the film by tilting 200 MeV Au-ion beams off the c-axis by ± 15°. The enhancement of the glass-liquid transition temperature and the increment of the dynamic critical exponent z were observed after the irradiation. The depinning model taking into account a distribution of pinning strength can reasonably describe the origin of the changes of both the glass-liquid transition temperature and z owing to the introduction of defects. This fact indicates that the flux line dynamics is governed by the pinning interaction rather than the intrinsic property of the flux line system.