We introduce a type of vortex entry edge barrier which controls the critical current in a perpendicular magnetic field in thin-film weak-pinning superconducting strips. Measurements of the critical current in thin-film amorphous-MoGe strips show a linear decrease with increasing magnetic field strength at low magnetic fields, and a crossover at a well-defined threshold field to an inverse power-law decay that is independent of the strip width. This behavior has not been observed previously due to bulk pinning, which only becomes dominant in our MoGe samples at high magnetic fields. To describe our results, we present calculations of the current distribution in thin superconducting strips with a finite penetration depth and negligible bulk pinning, and show that the measured critical currents in our MoGe samples correspond to a current density at the strip edge which approaches the Ginzburg-Landau depairing limit. Shape variations and defects along the strip edges influence the vortex entry conditions, leading to deviations from the ideal behavior, including offsets in the critical current maximum with respect to zero field.

• Received 17 November 2000

DOI:https://doi.org/10.1103/PhysRevB.64.014503