Superconducting gap nodal surface and fermi surface: their partial overlap in cuprates

Abstract

Electron correlation in cuprates leads to a global constraint ∑_k Δ_k=0 on the gap function Δ_k, resulting in a gap nodal surface. We give numerical results and qualitative physical arguments supported by some experimental results to argue that correlations also lead to a local constraint on charge fluctuations in k-space close to the Fermi surface, which may result in a substantial overlap of the Fermi surface with the gap nodal surface.