WHAT DOES INTRINSIC JOSEPHSON COUPLING SAY ABOUT THE PAIRING SYMMETRYIN THE CUPRATES

Measurements of the c-axis properties of the cuprate superconductors s how anomalous behavior in both normal and superconducting states. In p articular, there is strong evidence that pairs of CuO2 planes in neigh boring unit cells act as Josephson junctions below the critical temper ature T-c. We present a theory based on incoherent transport along the c-axis which naturally reproduces the anisotropic normal-state resist ivity and the superconducting-state Josephson coupling. Applying this theory to YBa2Cu3O7-delta (YBCO), we make quantitative predictions for the strength and temperature dependence of the Josephson coupling as well as the variation of T-c with disorder. Beyond the expected low-te mperature behavior, the Josephson critical current does not make a cle an separation between s- and d-wave superconductors, but the disorder- induced T-c variation does. Further experimental and theoretical work along these lines may therefore help determine the order parameter sym metry in the cuprates.