Fluctuation effects and order parameter symmetry in the cuprate superconductors

The effect of phase fluctuations on superconducting states with anisotropic order parameters is studied in a BCS-like lattice model of cuprate superconductors. The degradation of the mean-field transition temperature due to phase fluctuations is estimated within a Kosterlitz-Thouless scenario. Values of the interaction parameters for optimal doping, corresponding to a stable superconducting state of Sxy symmetry, which fit the nodal structure of the superconducting order parameter in the Bi2212 compound, are obtained. The angular position of the node is found to be insensitive to the dopant concentration. (orig.)