Inter-layer Superconducting Pairing Induced c-axis Nodal Lines in Iron-based Superconductors

TL;DR

This paper proposes that inter-layer pairing in iron-based superconductors can induce c-axis nodal lines, explaining observed gap modulations and predicting anti-correlated behaviors in different Fermi surface pockets.

Contribution

It introduces a mechanism where inter-layer pairing causes nodal lines in iron-based superconductors, linking quasi-3D behavior to observed gap features.

Findings

Inter-layer pairing induces c-axis nodal lines.

Explains observed c-axis gap modulations in ARPES data.

Predicts anti-correlated gap modulations in hole and electron pockets.

Abstract

A layered superconductor with a full pairing energy gap can be driven into a nodal superconducting (SC) state by inter-layer pairing when the SC state becomes more quasi-3D. We propose that this mechanism is responsible for the observed nodal behavior in a class of iron-based SCs. We show that the intra- and inter-layer pairings generally compete and the gap nodes develop on one of the {\em hole} Fermi surface pockets as they become larger in the iron-pnictides. Our results provide a natural explanation of the c-axis gap modulations and gap nodes observed by angle resolved photoemission spectroscopy. Moreover, we predict that an anti-correlated c-axis gap modulations on the hole and electron pockets should be observable in the $S^{\pm}$-wave pairing state.