Current-voltage characteristics of diluted Josephson-junction arrays: Scaling behavior at current and percolation threshold

Dynamical simulations and scaling arguments are used to study the current-voltage (I-V) characteristics of a two-dimensional model of resistively shunted Josephson-junction arrays in presence of percolative disorder, at zero external field. Two different limits of the Josephson-coupling concentration p are considered, where pc is the percolation threshold. For p>pc and zero temperature, the I-V curves show power-law behavior above a disorder-dependent critical current. The power-law behavior and critical exponents are consistent with a simple scaling analysis. At pc and finite temperature T, the results show the scaling behavior of a T=0 superconducting transition. The resistance is linear but vanishes for decreasing T with an apparent exponential behavior. Crossover to nonlinearity appears at currents proportional to T1+νT, with a thermal-correlation length exponent νT consistent with the corresponding value for the diluted XY model at pc. copyright 1997 The American Physical Society