Revealing the nature of the charge density wave order of ErTe$_3$ via Raman scattering under anisotropic strain

TL;DR

This study uses Raman scattering under anisotropic strain to investigate the unconventional charge density wave order in ErTe3, revealing that a single component CDW with a tilted wavevector explains observed symmetry breakings.

Contribution

It demonstrates that a single component CDW with a tilted wavevector accounts for mirror symmetry breaking, challenging previous ferro-axial multi-component models.

Findings

Mirror symmetry breakings are linked to a single component CDW with a tilted wavevector.

Raman spectra support a model with a single, tilted CDW order parameter.

The unconventional CDW in ErTe3 involves mirror symmetry breaking explained by strain-dependent Raman data.

Abstract

The nature of the charge density wave (CDW) order of the rare-earth tritelluride ErTe3 is investigated by Raman scattering under anisotropic strain. The CDW state of ErTe3 is unconventional since it is accompanied by an unusual mirror symmetry breaking, whose origin remains to be understood. Studying the polarization-resolved Raman spectrum of the CDW amplitude mode as a function of strain and temperature, we find that the mirror symmetry breakings of the CDW state are not independent, arguing against the recently proposed ferro-axial multi-component CDW order. Instead, we show that a single component CDW order parameter with an ordering wavevector tilted away from the principle crystallographic axis can reproduce the observed mirror symmetry breakings and their manifestation in the Raman spectra.