Phase-coherence transition in granular superconductors with pi junctions

We study the three-dimensional XY-spin glass as a model for the resistive b ehavior of granular superconductors containing a random distribution of pi junctions, as in high-T-c superconducting materials with d-wave symmetry. T he pi junctions leads to quenched in circulating currents (chiralities) and to a chiral-glass state at low temperatures, even in the absence of an ext ernal magnetic field. Dynamical simulations in the phase representation are used to determine the nonlinear current-voltage characteristics as a funct ion of temperature. Based on dynamic scaling analysis, we find a phase-cohe rence transition at finite temperature below which the linear resistivity s hould vanish and determine the corresponding critical exponents. The result s suggest that the phase and chiralities may order simultaneously for decre asing temperatures into a superconducting chiral-glass state. (C) 2001 Else vier Science B.V. All rights reserved.