Resistive transition in two-dimensional arrays of superconducting weak links

We present results of measurements on large arrays of PbBi/Cu proximity-effect junctions. Extrapolation of the critical current measured at low temperature to the region at and above Tc allows us to describe the initial drop in resistance by a simple model of the proximity effect, and also to define an appropriate effective temperature ̃ \~TEJ(Tc)TEJ(T) for describing the vortex-unbinding transition. Nonlinear I-V curves above Tc are described by a crossover function whose form is consistent with the theory of Halperin and Nelson.