Critical currents in Al films with a triangular lattice of 1 µm holes

Critical currents have been measured in an Al film perforated with a two-dimensional triangular lattice pattern of holes. A pulsed current technique has been used to determine the interaction between the vortex lattice and the hole lattice as a function of temperature and magnetic field. Enhanced critical currents of the perforated specimen, compared to critical currents of a similar unperforated reference specimen, are a result of the strong pinning forces at the edges of the holes which tend to trap the cores of the vortices in the holes. When the flux density matches the hole density, the coherent operation of the vortex hole coupling forces is observed to withstand a driving force from the applied current which approaches the theoretical maximum current carrying capacity of a superconductor. At low temperatures, fast pulse measurements reveal that the super-normal instability transitions tend to be suppressed by the application of a magnetic field, allowing the determination of the flux flow thresholds at temperatures well below Tc.