Anisotropic Linear Optical Properties and Optical Resonances in Weyl Semimetals*

Since the first experimental discovery of Weyl semimetals, TaAs and NbAs have attracted significant attention due to their broken inversion symmetry and topological properties. Optical characterization serves as a powerful tool to probe electronic transitions in these systems. To understand optical response as a function of wavelength, the anisotropic dielectric functions and complex refractive indices serve as fundamental properties and vital pieces of the puzzle.

Here, we demonstrate a comprehensive study of anisotropic dielectric functions of TaAs and NbAs by combining spectroscopic ellipsometry and density functional theory (DFT). The complete set of Lorentz oscillators reveals complicated resonances in the system. Multiple resonances are observed near several probing wavelengths, enhancing the optical response. Furthermore, the contributions by two types of Weyl points to dielectric functions show dominating response in low energy regions but are insignificant above 1 eV compared to the contributions from trivial bands.