TAO pairing: a fully gapped pairing scenario for the Iron-Based Superconductors

TL;DR

This paper proposes a novel fully gapped, topological superconducting pairing scenario for iron-based superconductors, involving orbital triplet states that transform as s-wave pairs, with predicted Raman-active excitations.

Contribution

It introduces a new orbital triplet pairing mechanism that results in a fully gapped, topological superconductor in iron-based materials, expanding understanding of their pairing symmetry.

Findings

Orbital triplet d-wave states can form s-wave pairs under certain rotations.

The proposed pairing leads to a fully gapped, topological superconducting state.

Raman-active excitations are predicted below the transition temperature.

Abstract

Motivated by the fully gapped superconductivity in iron-based superconductors with uncompensated electron pockets, we propose a spin singlet, but orbital triplet analogue of the superfluid phase of He-3B. We show that orbital triplets with a nominal d-wave symmetry at the iron sites can transform as s-wave pairs under rotations about the selenium sites. Linear combinations of such d$_{xy}$ and d$_{x^{2}-y^{2}}$ triplets form a fully gapped, topological superconductor. Raman-active excitations are predicted to develop below the superconducting transition temperature.