Coexistence of Antiferromagnetism and Superconductivity in Iron-Based Superconductors

TL;DR

This paper theoretically explores the coexistence of antiferromagnetism and superconductivity in iron-based superconductors, revealing how different pairing symmetries affect the superconducting gap structure on various Fermi surfaces.

Contribution

It demonstrates that both s_{+-} and s_{++} pairing symmetries can coexist with antiferromagnetism and analyzes the resulting gap structures on Dirac and non-Dirac Fermi surfaces.

Findings

Both s_{+-} and s_{++} waves can coexist with antiferromagnetism.

Superconducting gap has nodes for s_{++} on Dirac Fermi surfaces.

Gap structure varies on non-Dirac surfaces depending on pairing parameters.

Abstract

We theoretically investigate the coexistence of antiferromagnetism and superconductivity in the iron-based superconductors by using the mean-field theory for two- and three-orbital models. We find that both the s_{+-}-wave and s_{++}-wave superconductivity can coexist with antiferromagnetism in the two models. On Dirac Fermi surfaces emerging in the antiferromagnetic phase, a superconducting-gap function has a node for s_{++} wave but is nodeless for s_{+-} wave. On the other hand, the gap function on non-Dirac Fermi surfaces is either nodeless or accidentally nodal, depending on the parameters of pairing interaction, which is independent of pairing symmetry.