Stress-induced nematicity in EuFe2As2 studied by phononic Raman spectroscopy

TL;DR

This study uses polarized Raman scattering to investigate how strain affects nematicity and structural phase transitions in EuFe2As2, revealing strain-induced symmetry breaking above the transition temperature.

Contribution

It demonstrates that surface strain can induce nematicity and symmetry breaking in EuFe2As2, providing insights into the interplay between strain and electronic nematic phases.

Findings

Surface polishing preserves intrinsic transition temperature.

Strain from cutting induces symmetry breaking above Ts.

Nematicity can be strain-induced and is detectable via Raman spectroscopy.

Abstract

We use polarized Raman scattering to study the structural phase transition in EuFe2As2, the parent compound of the 122-ferropnictide superconductors. The in-plane lattice anisotropy is characterized by measurements of the side surface with different strains induced using different preparation methods. We show that while a fine surface polishing leaves the samples free of residual internal strain, in which case the onset of the C4 symmetry breaking is observed at the nominal structural phase transition temperature Ts, cutting the side surface induces a permanent four-fold rotational symmetry C4 breaking spanning tens of degrees above Ts.