Electrical resistivity and magnetic susceptibility roundings above the superconducting transition in Y₁Ba₂Cu₃O_{7- delta}

Abstract

The authors report high-resolution data of the electrical resistivity and of the magnetic susceptibility rounding effects above the superconducting transition in single-phase polycrystalline YBa2Cu3O 7- delta compounds. These data may be explained quantitatively and consistently, over two orders of magnitude in reduced temperature, by direct three-dimensional thermodynamic fluctuations of the amplitude of a two-component order parameter in unconventional (non-s-wave pairing) superconductors. The resulting order parameter correlation length amplitudes are xi ab(0)=(12+or-3) AA, and xi perpendicular to(0)=(1.4+or-0. 4) AA, the Lawrence-Doniach effective interlayer distance is d c=(8+or-2) AA, and the Ginzburg reduced temperature is epsilon G=(0.7+or-0.3)*10-2.