Influence of Spin Orbit Coupling in the Iron-Based Superconductors

TL;DR

This study investigates how spin-orbit coupling affects the electronic structure of iron-based superconductors, revealing its significant impact on hole pockets and challenging existing theories of their pairing mechanisms.

Contribution

It combines experimental photoemission spectroscopy with theoretical calculations to demonstrate the widespread influence of SOC in Fe-based superconductors, especially on the superconducting gap.

Findings

SOC modifies the electronic structure in FeSCs

SOC effects are concentrated on hole pockets

Results challenge pure spin-singlet pairing models

Abstract

We report on the influence of spin-orbit coupling (SOC) in the Fe-based superconductors (FeSCs) via application of circularly-polarized spin and angle-resolved photoemission spectroscopy. We combine this technique in representative members of both the Fe-pnictides and Fe-chalcogenides with ab initio density functional theory and tight-binding calculations to establish an ubiquitous modification of the electronic structure in these materials imbued by SOC. The influence of SOC is found to be concentrated on the hole pockets where the superconducting gap is generally found to be largest. This result contests descriptions of superconductivity in these materials in terms of pure spin-singlet eigenstates, raising questions regarding the possible pairing mechanisms and role of SOC therein.