Transport Properties of Granular High-TC Superconductors

We report on the application of the Resistively Shunted Junction (RSJ) model to granular high TC superconductors. Some derived predictions of the RSJ model are applied to a set of superconducting granular samples which can be considered as a network of Josephson junctions. The investigated samples belong to both holedoped Y1ixPrxBa2Cu3O7id (x = 0.0, 0.35, and 0.45) and the electron-doped Sm2ixCexCuO4id (x = 0:18) systems which display the so-called double resistive superconducting transition. We have performed several transport measurements in these compounds including temperature and magnetic field dependence of the electrical resistance, R(T; H), and I-V characteristics. Several aspects of the I-V characteristics were quantitatively well described by the RSJ model. The combined results strongly suggest that dissipation in granular superconducting samples is a natural consequence of the normal current flowing in parallel with the supercurrent current.