Anisotropie Cooper Pairs in High-Tc Superconductors

Abstract

Anisotropic Cooper pairs in high-T _c superconductors are theoretically examined by assuming two types of attractive interactions such as a superexchange interaction working between the nearest neighbor unit cells, and breathing modes of oxygen octahedrons working as attractive interactions between the second and third neighbors. Cooper pairs with d-symmetry are most probable because of strong on-site repulsive interactions. If the super exchange is the most effective, especially, the shape of Fermi surface, which is characteristic of the van Hove singularity, definitely favors Cooper pairs with dγ-symmetry (k _x ²-k _y ²).