Discerning the Vibrational Nature of ReS2 Raman Modes Using Solid-Angle-Resolved Raman Spectroscopy

ReS 2 exhibits reduced crystal symmetry, which leads to pronounced anisotropy and intricate Raman vibrations. However, to date, the vibrational nature of ReS 2 Raman modes has remained elusive, with unresolved theoretical disputes. Here, we study Raman vibrations in ReS 2 crystals using solid-angle-resolved Raman spectroscopy, which allows us to leverage the full 3 × 3 Raman tensor to resolve the A g -like and E g -like nature of all the 18 Raman modes. Combined with pressure-dependent measurements, we observe distinct behavior in the A g -like and E g -like modes. Our findings show unambiguous experimental evidence for discerning the ReS 2 Raman modes and can offer important insights into the vibrational nature of Raman modes in layered anisotropic crystals.