Raman study of lattice dynamics in Weyl semimetal TaAs

TL;DR

This study uses polarized Raman spectroscopy to investigate lattice vibrations in the Weyl semimetal TaAs, confirming phonon modes and identifying multi-phonon excitations, with some unexplained spectral features.

Contribution

First-principles calculations combined with Raman measurements provide a detailed understanding of phonon modes and multi-phonon excitations in TaAs.

Findings

All optical phonons observed match theoretical predictions.

Multiple-phonon excitations detected and characterized.

Unexplained spectral background component identified.

Abstract

We report a polarized Raman study of Weyl semimetal TaAs. We observe all the optical phonons, with energies and symmetries consistent with our first-principles calculations. We detect additional excitations assigned to multiple-phonon excitations. These excitations are accompanied by broad peaks separated by 140~cm$^{-1}$ that are also most likely associated with multiple-phonon excitations. We also noticed a sizable B$_1$ component for the spectral background, for which the origin remains unclear.