Correlation between Superconductivity and Magnetic Fluctuations in Fe(Se1-xSx) Revealed by 77Se NMR

TL;DR

This study uses 77Se NMR to explore how magnetic fluctuations relate to superconductivity in FeSe$_{1-x}$S$_x$, revealing that magnetic fluctuations correlate with $T_c$ and are crucial for superconductivity.

Contribution

It demonstrates the correlation between magnetic fluctuations and superconductivity across different sulfur doping levels in FeSe$_{1-x}$S$_x$, highlighting the importance of magnetic fluctuations.

Findings

Magnetic fluctuations are enhanced at low sulfur content.

Magnetic fluctuations are suppressed at higher sulfur content.

Superconducting transition temperature $T_c$ correlates with magnetic fluctuations.

Abstract

We present $^{77}$Se-NMR measurements on FeSe$_{1-x}$S$_x$ samples with sulfur content $x=0,9,15$ and $29\%$. Twinned nematic domains are observed in the NMR spectrum for all samples except $x=29\%$. The NMR spin-lattice relaxation rate shows that magnetic fluctuations are initially enhanced between $x=0\%$ and $x=9\%$, but are strongly suppressed for higher $x$ values. The observed behavior of the magnetic fluctuations parallels the superconducting transition temperature $T_c$ in these materials, providing strong evidence for the primary importance of magnetic fluctuations for superconductivity, despite the presence of nematic quantum criticality in this system.