Observation of Ising spin-nematic order and its close relationship to the superconductivity in FeSe single crystals

TL;DR

This study reports the detection of Ising spin-nematic order in FeSe single crystals and reveals a universal linear relationship between the nematic ordering temperature and superconducting transition temperature, suggesting a shared microscopic origin.

Contribution

It provides direct experimental evidence of Ising spin-nematic order in FeSe and links it to superconductivity through a universal Tc-Tsn relationship.

Findings

Identification of Ising spin-nematic order via magnetoresistance and magnetization measurements.

Observation of a universal linear relationship between Tc and Tsn in FeSe samples.

Evidence that spin nematicity and superconductivity share a common microscopic origin.

Abstract

Superconducting FeSe single crystals of (001) orientation are synthesized via a hydrothermal ion-release route. An Ising spin-nematic order is identified by our systematic measurements of in-plane angular-dependent magnetoresistance (AMR) and static magnetization. The turn-on temperature of anisotropic AMR signifies the Ising spin-nematic ordering temperature Tsn, below which a two-fold rotational symmetry is observed in the iron plane. A downward curvature appears below Tsn in the temperature dependence of static magnetization for the weak in-plane magnetic field as reported previously. Remarkably, we find a universal linear relationship between Tc and Tsn among various superconducting samples, indicating that the spin nematicity and the superconductivity in FeSe have a common microscopic origin.