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 Josep hson-junction array in a magnetic field are considered. For rational v alues of the average flux quantum per plaquette f, the superconducting transition temperature vanishes, for increasing dilution at a critica l 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 percolat ion threshold. For x(VL) < x < x(p), the array behaves as a zero-tempe rature vortex glass. Numerical results for f = 1/2 from defect energy calculations are presented and are consistent with this scenario. [S01 63-1829(98)00818-2].