PHASE DYNAMICS IN PERCOLATING JOSEPHSON-JUNCTION ARRAYS

The temperature-dependent helicity modulus Gamma(T) of site-diluted tr iangular arrays of proximity-effect coupled Pb/Cu/Pb Josephson junctio ns has been extracted from measurements of the complex ac sheet conduc tance performed in the frequency range 0.1 Hz to 20 kHz in zero magnet ic field. At low frequencies Gamma(T) exhibits the characteristic supe rfluid drop predicted by the Kosterlitz-Thouless theory, demonstrating that a disordered array behaves like a homogeneous two-dimensional sy stem at length scales larger than the percolation correlation length.