Dielectric property of MoS_2 crystal in terahertz and visible regions

Two-dimensional materials such as MoS2 have attracted much attention in recent years due to their fascinating optoelectronic properties. The dielectric response of MoS2 crystal in both the terahertz (THz) and visible regions is studied in this work. Time-domain THz spectroscopy is employed for the THz property investigation. The real and imaginary parts of the complex dielectric constant of MoS2 crystal are found to follow a Drude model, which is due to the intrinsic carrier absorption. In the visible region, ellipsometry is used to investigate the dielectric response. The general trend of the complex dielectric constant is found to be described with a Lorentz model, while two remarkable dielectric response peaks are observed to be located at 1.85 and 2.03 eV, which has been attributed to the splitting arising from the combined effect of interlayer coupling and spin-orbit coupling. This work can be the research foundation for future optoelectronic applications with MoS2.