Observation of low-frequency Raman peak in layered WTe 2

WTe 2 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 WTe 2 , 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.