Diluted Josephson-junction arrays in a magnetic field: phase coherence and vortex glass thresholds

Abstract

The effects of random dilution of junctions on a two-dimensional Josephson-junction array in a magnetic field are considered. For rational values of the average flux quantum per plaquette f, the superconducting transition temperature vanishes, for increasing dilution at a critical value x_S(f), while the vortex ordering remains stable up to x_VL > x_S, far below the value x_p corresponding to the geometric percolation threshold. For x_VL < x < x_p, the array behaves as a zero-temperature vortex glass. Numerical results for f=½ from defect energy calculations are presented and are consistent with this scenario.