DISSIPATION IN A WEAK-LINK-LIMITED SUPERCONDUCTOR AS A PROBLEM OF PERCOLATION THEORY

Broadening of the resistive transition of sintered GdBa2Cu3O7-x superc onductor has been studied varying the measuring current over the range of five orders of magnitude. The observed well-defined branching poin ts in the resistive transition coincide with the quasi-Ohmic saturatio n of V-I curves and scale with the average grain size. The results sug gest the validity of a simple percolation model for dissipation in sys tems whose global superconductivity is realized by Josephson coupling of the superconducting grains. A common origin of structured resistive transition, observed in many superconducting systems, has been also d iscussed.