Strong anisotropic optical response in two-dimensional Mo-VIA and Mo-VIIA monolayer binary materials

Abstract

Two-dimensional binary materials based on transition metals have attracted much research attention because of their intriguing physical properties owing to their crystalline structure. The optical response of these compounds paves a way to manipulate the optical and electronic properties for optical and electronic device applications. Here, the frequency-dependent anisotropic linear optical response of eight molybdenum (Mo)-based binary materials from the VIA (i.e., O, S, Se, and Te) and VIIA (i.e., F, Cl, Br, and I) groups are systematically investigated using first-principles density functional theory. These binary materials exhibit strong linear anisotropic dielectric and optical behavior in the low energy range and become isotropic at high energies. The linear anisotropy in optical functions can be attributed to the intralayer excitonic behavior. The phenomenon of birefringence is the main characteristic of anisotropic materials. The dichroic ratio determines the degree of anisotropy. Among these binary materials, MoS2 and MoCl2 show large birefringence in the visible and far-infrared regions. The birefringence in these materials is also compared with other reported materials. Birefringence is critical for light manipulation during propagation through media. The present results provide insight into the linear optical anisotropies of the binary materials considered. Furthermore, the results suggest that these Mo-based binary materials could be potential candidates for developing optical instruments, optoelectronic, and photonic device applications.