Observation of low-frequency Raman peak in layered WTe2

WTe2 recently attracted considerable attention as a layered material exhibiting ferroelectricity, giant magnetoresistance, and pressure-induced superconductivity. In this study, we performed Raman spectroscopy on bulk WTe2, including the low-frequency region. An unfamiliar Raman peak (P0) was found at approximately 9 cm(-1) in addition to the seven already known peaks (P1-P7). Furthermore, the angular and polarization dependence of the spectra revealed the peak P0 had A(1) symmetry. The symmetry is consistent with the experimental results and first-principles calculations by other groups. Our work paves the way for studying the symmetry of the low-frequency phonons in atomic-layer ferrolectric films using Raman spectroscopy.