STABILITY OF D-WAVE PAIRING IN 2 DIMENSIONS

A nearest neighbours pairing interaction favours a state of d(x)2(-y)2 symmetry in cuprate superconductors. Within weak coupling pairing the ory this d(x)2(-y)2 state is remarkably stable with respect to changes in the bandstructure which respect the square lattice symmetry, the p resence of next-neighbour pairing interactions, or doping level about half filling. Strong next neighbour pairing interactions stabilize nod eless mixed states such as d(x)2(-y)2 + id(xy). Orthorhombic distortio n, on the other hand, leads to a nodeful d+/-s state. Consequences for realistic theories of cuprate superconductors are discussed.