Chiral phonons in sixfold chiral CrSi$_2$: Raman spectroscopy and first-principles calculations

TL;DR

This study demonstrates the existence of chiral phonons in sixfold chiral CrSi$_2$ crystals through Raman spectroscopy and first-principles calculations, broadening the understanding of chiral vibrational modes.

Contribution

It provides the first evidence of chiral phonons in a sixfold chiral crystal, expanding the scope beyond trigonal symmetry materials.

Findings

Circularly polarized Raman spectroscopy revealed splitting of $E_2$ phonon modes.

First-principles calculations supported the experimental observations.

Chiral phonons are present in CrSi$_2$, a sixfold chiral crystal.

Abstract

Chiral phonons have been identified in several chiral crystals, primarily in those with trigonal symmetry and threefold screw axes. In this study, chiral phonons in CrSi$_2$, a chiral crystal with a sixfold helical structure, were investigated. Circularly polarized Raman spectroscopy revealed a subtle splitting of doubly degenerate $E_2$ phonon modes between cross-circular polarization configurations. These observations, supported by first-principles phonon calculations, indicate the presence of chiral phonons in CrSi$_2$, expanding the scope of materials that exhibit chiral vibrational modes beyond the conventional trigonal class.