Spin excitations and the Fermi surface of superconducting FeS

Haoran Man,Yu Song,Zhiping Yin,Rui Zhang,Luis Balicas,David J Singh,Leland Harriger,Qimiao Si,Weiyi Wang,Jiangang Guo,Tillman Hickel ,R Schönemann ,M B Stone ,Ilya Eremin ,Morgan Fu ,J W Lynn ,Q Huang ,C Broholm ,Felix Lochner,Pengcheng Dai

doi:10.1038/s41535-017-0019-6

Abstract

High-temperature superconductivity occurs near antiferromagnetic instabilities and the nematic state. Debate remains on the origin of nematic order in FeSe and its relation with superconductivity. Here, we use transport, neutron scattering and Fermi surface measurements to demonstrate that hydrothermo grown superconducting FeS, an isostructure of FeSe, is a tetragonal paramagnet without nematic order and with a quasiparticle mass significantly reduced from that of FeSe. Only stripe-type spin excitations are observed up to 100 meV. No direct coupling between spin excitations and superconductivity in FeS is found, suggesting that FeS is less correlated and the nematic order in FeSe is due to competing checkerboard and stripe spin fluctuations.

Highlights

We use transport (Fig. 1), neutron scattering (Figs. 2 and 3), quantum oscillation experiments (Fig. 4), as well as density function theory (DFT)[27] and DFT combined with dynamical mean field theory (DMFT) calculations[28, 29] to study single crystals of FeS
We conclude that FeS has no nematic order, which is consistent with the previous reports on FeS23, 24 and with the notion that the nematic phase vanishes for FeSe1−xSx for x ≥ 0.17.31–33 The results from the transport measurements are complemented by those from elastic neutron scattering measurements, which reveal that the system is paramagnetic at all temperatures, suggesting that the previous observation of magnetic order in FeS is likely due to impurity phases.[34, 35]
Having established the absence of any nematic order in FeS, we turn to probing the spin excitation spectrum by inelastic neutron scattering experiments

Summary

Introduction

These properties suggest that FeS is a weakly correlated analog of FeSe and, that the nematic order in FeSe is due to the frustrated magnetic interactions underlying the competing checkerboard and stripe spin fluctuations.[16,17,18]

Methods

Results

Conclusion