Defects produced by removing small numbers of junctions in a square Josephson-junction array act as strong vortex-pinning sites. We find the vortex-depinning current for various types of isolated defects with numerical simulations of the static phase configuration, and present arguments for the dependence of depinning current on defect size. We also discuss pinning of multiple vortices on a single defect, and generalize our results to systems containing many defects.

• Received 12 December 1990

DOI:https://doi.org/10.1103/PhysRevB.43.12823