Origin of the Resistivity Anisotropy in the Nematic Phase of FeSe

TL;DR

This study investigates the origin of resistivity anisotropy in FeSe's nematic phase, revealing it is mainly caused by anisotropic spin fluctuations rather than magnetic order, with the anisotropy peaking near the structural transition.

Contribution

It provides the first detailed analysis disentangling nematic and magnetic contributions to resistivity anisotropy in FeSe, emphasizing the role of spin fluctuations.

Findings

Resistivity anisotropy peaks below the structural transition temperature.

Anisotropy diminishes to nearly zero at the superconducting transition.

Inelastic scattering by anisotropic spin fluctuations dominates the anisotropy.

Abstract

The in-plane resistivity anisotropy is studied in strain-detwinned single crystals of FeSe. In contrast to other iron-based superconductors, FeSe does not develop long-range magnetic order below the nematic/structural transition at $T_{s}\approx$90~K. This allows for the disentanglement of the contributions to the resistivity anisotropy due to nematic and magnetic orders. Comparing direct transport and elastoresistivity measurements, we extract the intrinsic resistivity anisotropy of strain-free samples. The anisotropy peaks slightly below $T_{s}$ and decreases to nearly zero on cooling down to the superconducting transition. This behavior is consistent with a scenario in which the in-plane resistivity anisotropy in FeSe is dominated by inelastic scattering by anisotropic spin fluctuations.