DILUTED JOSEPHSON-JUNCTION ARRAYS IN A MAGNETIC FIELD : PHASE COHERENCE AND VORTEX GLASS THRESHOLDS

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 ${x}_{\mathrm{VL}}g{x}_{S},$ far below the value ${x}_{p}$ corresponding to the geometric percolation threshold. For ${x}_{\mathrm{VL}}lxl{x}_{p},$ the array behaves as a zero-temperature vortex glass. Numerical results for $f=1/2$ from defect energy calculations are presented and are consistent with this scenario.