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 $T_c$ 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 $\tilde{T}\cong \frac{E_J\left(T_c\right)T}{E_J\mathrm{}\left(T\right)\mathrm{}}$ for describing the vortex-unbinding transition. Nonlinear $I-V$ curves above $T_c$ are described by a crossover function whose form is consistent with the theory of Halperin and Nelson.