Higher anisotropic d-wave symmetry in cuprate superconductors

We derive a pair potential from tight binding further neighbour attraction that leads to superconducting gap symmetry similar to that of the phenomenological spin fluctuation theory of high temperature superconductors (Monthoux et al 1991 Phys. Rev. Lett. 67 3448). We show that higher anisotropic d-wave than the simplest d-wave symmetry is one of the important ingredients responsible for higher BCS characteristic ratio. (author). Letter-to-the-editor