Raman tensor of layered black arsenic

Due to the similar atom arrangement with black phosphorus, black arsenic also has obvious Raman anisotropy at both the base and cross planes. However, the polarization characteristics of black arsenic have been rarely reported so far with most relevant studies devoted to the base plane. Here, to compensate for the blank of the anisotropy in cross plane, we implemented a systematical angle‐resolved polarized Raman measurement on both planes of layered black arsenic and observed that the Raman intensity ratios (Ixx : Iyy : Izz) of optical phonons Ag1 and Ag2 modes along different axes are 1:4.8:2.76 and 6.9:1:5.7, respectively. Based on the definition of Raman intensity, we ed integral Raman tensors of black arsenic. In addition, according to density functional theory, it can be affirmed that the Raman anisotropy of Ag mode is sourced from the anisotropy of differential polarizability along different crystal axes.