Nodal superconductivity in FeS: Evidence from quasiparticle heat transport

TL;DR

This study presents heat transport measurements on FeS, revealing evidence of nodal superconductivity, which enhances understanding of pairing mechanisms in iron-based superconductors with similar structures.

Contribution

It provides the first direct evidence of nodal superconducting gap in FeS through heat transport experiments, comparing it with FeSe and other iron-based superconductors.

Findings

Significant residual linear term in heat conductivity at zero field

Rapid increase of residual heat conductivity with magnetic field

Evidence supporting nodal superconducting gap in FeS

Abstract

We report low-temperature heat transport measurements on superconducting iron sulfide FeS with $T_c \approx$ 5 K, which has the same crystal structure and similar electronic band structure to the superconducting iron selenide FeSe. In zero magnetic field, a significant residual linear term $\kappa_0/T$ is observed. At low field, $\kappa_0/T$ increases rapidly with the increase of field. These results provide strong evidence for nodal superconducting gap in FeS. We compare it with the sister compound FeSe, and other iron-based superconductors with nodal gap.