Superconducting Gap Nodal Surface and Fermi Surface: their partial overlap in cuprates

TL;DR

This paper explores how electron correlations in cuprates create a gap nodal surface and suggests that these correlations also cause the Fermi surface to partially overlap with this nodal surface, affecting charge fluctuations.

Contribution

It introduces the idea that local constraints from correlations lead to a significant overlap between the Fermi surface and the gap nodal surface in cuprates.

Findings

Global constraint on gap function due to correlations

Numerical and experimental support for local charge fluctuation constraints

Overlap of Fermi surface with gap nodal surface in cuprates

Abstract

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