Role of Nematic Fluctuations on Superconductivity in FeSe$_{0.47}$Te$_{0.53}$ Revealed by NMR under Pressure

TL;DR

This study uses NMR under pressure to explore how nematic fluctuations influence superconductivity in FeSe$_{0.47}$Te$_{0.53}$, revealing that nematic fluctuations are more crucial than antiferromagnetic spin fluctuations near the nematic quantum critical point.

Contribution

It provides experimental evidence that nematic fluctuations predominantly drive superconductivity in FeSe$_{1-x}$Te$_{x}$ near the nematic QCP, contrasting with other iron-based superconductors.

Findings

Superconducting Tc and AFMSF increase under pressure.

AFMSF contributes less to SC in FeSe$_{0.47}$Te$_{0.53}$ than in FeSe$_{1-x}$S$_{x}$.

Nematic fluctuations are the dominant factor for SC near the nematic QCP.

Abstract

The relationship between antiferromagnetic (AFM) spin fluctuations (SF), nematic fluctuations, and superconductivity (SC) has been central to understanding the pairing mechanism in iron-based superconductors (IBSCs). Iron chalcogenides, which hold the simplest crystal structure in IBSCs, provide a good platform to investigate the relationship. Here, we report $^{77}$Se and $^{125}$Te nuclear magnetic resonance studies of FeSe$_{0.47}$Te$_{0.53}$, which is located close to a nematic quantum critical point (QCP), under pressures up to 1.35 GPa. Both the superconducting critical temperature and AFMSF were found to be enhanced under pressure, which suggests a correlation between SC and AFMSF in FeSe$_{0.47}$Te$_{0.53}$. However, the contribution of AFMSF to SC in FeSe$_{0.47}$Te$_{0.53}$ was found to be much less compared to that in FeSe$_{1-x}$S$_{x}$, suggesting that nematic fluctuations play a dominant role in the SC in FeSe$_{1-x}$Te$_{x}$ around the nematic QCP.