Spin fluctuations in LiFeAs observed by neutron scattering

TL;DR

This study uses neutron scattering to investigate spin fluctuations in LiFeAs, revealing antiferromagnetic fluctuations and a resonance in the superconducting state, challenging some theoretical predictions and aligning with common mechanisms in iron-based superconductors.

Contribution

First neutron scattering measurements on LiFeAs showing magnetic fluctuations and resonance, providing insights into its superconducting mechanism.

Findings

Evidence of strong antiferromagnetic fluctuations.

Observation of a resonance in the superconducting state.

Results do not support spin-triplet p-wave superconductivity.

Abstract

We report neutron inelastic scattering measurements on the stoichiometric iron-based superconductor LiFeAs. We find evidence for (i) magnetic scattering consistent with strong antiferromagnetic fluctuations, and (ii) an increase in intensity in the superconducting state at low energies, similar to the resonant magnetic excitation observed in other iron-based superconductors. The results do not support a recent theoretical prediction of spin-triplet p-wave superconductivity in LiFeAs, and instead suggest that the mechanism of superconductivity is similar to that in the other iron-based superconductors.