Critical currents, pinning, and edge barriers in narrow ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ thin films

Current transport behavior is reported for narrow strips (down to approximately 1 μm) of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ thin films deposited and lithographically patterned by various means. A systematic increase in the critical current densities is observed in the narrowest strips, suggesting the possible presence of an edge barrier-to-flux entry in these films. The critical currents are found to be near the depairing limit as calculated for these particular films. The critical currents are observed to decrease with increasing temperature, consistent with a flux-creep model. Also, current-voltage characteristics are measured at various temperatures. These characteristics are consistent with exponential behavior in the low-temperature region, but are better fit by power-law behavior at the high temperatures. Flux-pinning energies at zero temperature derived from these data range from 20 to 200 meV depending on the method used. The high-temperature power-law behavior may reflect inhomogeneities along the length of the strips.