Orientation–polarization dependence of pressure-induced Raman anomalies in anisotropic 2D ReS₂

We report an in situ high-pressure (0–30.24 GPa) optical study of the 2D ReS₂ crystal under four specific configurations of sample orientation and laser polarization. Unlike the horizontal measurement configuration that has been widely used, under the vertical sample configuration we observe the anomalous disappearance behavior of Raman modes. Through analyzing the peak evolution under different configurations with tensor calculations, we identify the effect of pressure on different components in the full 3 × 3 Raman tensor of the anisotropic ReS₂ crystal. These results provide new evidence on the remarkable tunability of pressure engineering on the crystal structure, and our methods offer an additional degree of freedom for studying pressure engineering on 2D anisotropic materials.