Superconducting fluctuations and the Nernst effect in high-T-c superconductors

Abstract

The comprehensive rho(T) measurements and the consequent resistivity curvature mapping (RCM) on Y0.7Ca0.3Ba2Cu3O7-delta thin films (doping levels p = 0.08-0.21) elucidate a phase diagram for the whole doping range. This phase diagram further strengthens a view that the 'normal' phase in hole-doped cuprates should be divided into a strong superconducting (SC) fluctuation phase and the 'real' normal phase in which there is no significant influence of SC. The temperature of superconducting fluctuations T-f as a function of p was calculated using the Ginzburg-Landau model for layered superconductors. Comparisons between T-f and the Nernst temperature establish the origin of the Nernst effect as SC fluctuations. Some of the details in rho(T) cannot be fully understood by the existing models and call for a more sophisticated theory of carrier dynamics in cuprates.