Edwards-Anderson parameter and local Ising-nematicity in FeSe revealed via NMR spectral broadening

TL;DR

This study uses NMR spectral analysis to connect the broadening observed in FeSe with the Edwards-Anderson parameter, revealing insights into the nematic domain structure and its relation to nematic susceptibility under varying temperature and pressure.

Contribution

It provides a quantitative link between NMR broadening and the Edwards-Anderson parameter in an Ising-nematic model with disorder, clarifying the nematic behavior in FeSe.

Findings

NMR broadening correlates with the Edwards-Anderson parameter.

Results reconcile NMR and Raman spectroscopy data.

Broadening depends on temperature and pressure as predicted by the model.

Abstract

The NMR spectrum of FeSe shows a dramatic broadening on cooling towards the bulk nematic phase at $T_s=90$ K, due to the formation of a quasi-static, short-range-ordered nematic domain structure. However, a quantitative understanding of the NMR broadening and its relationship to the nematic susceptibility is still lacking. Here, we show that the temperature and pressure dependence of the broadening is in quantitative agreement with the mean-field Edwards-Anderson parameter of an Ising-nematic model in the presence of random-field disorder introduced by non-magnetic impurities. Furthermore, these results reconcile the interpretation of NMR and Raman spectroscopy data in FeSe under pressure.