d-wave Paraconductivity Characterization of Tc Variations in High-Tc Superconducting Films

The fluctuation conductivity above Tc (the paraconductiviy) in films of Bi2Sr2CaCu2O8+d (Bi2212) and YBa2Cu3O7-≏ (YBCO) with Tc variations is analyzed in terms of theoretical formulae based on the d-wave superconductivity. It is found that experimental data are describable by the Aslamazov-Larkin term provided that a total-energy cutoff effect is taken into account though there are deviations in the fits for the YBCO case, which can be improved by considering overall contributions to the paraconductivity. The dependence of the fluctuation amplitude upon Tc is reconciled with the d-wave theory.