Dynamical polarization and the optical response of silicene and related materials

Abstract

We discuss the dynamical polarization and optical response in low-frequency regime under in-plane polarized driving field of the silicene. The dynamical polarization, dielectric function, and absorption of radiation in infrared region are obtained and shown intuitively in the momentum-frequency space. They are found distinguishing for the cases that chemical potential larger than the band gap and chemical potential smaller than the band gap. The optical properties of silicene and the related group-V and group-VI materials: MoS2 and black phosphorus are explored through the first-principle study. The plasmon, which is a collective mode, damped into the electron-hole pair in the single-particle excitation regime, and the spin/valley polarized electron-hole pairs can also be formed through this way, especially for the high-energy π-plasmon which begin to damp even in the long-wavelength limit. The plasmon can also be observed in the spectrum of the energy-loss function in infrared region. The anisotropic effect due to the warping structure or the charged impurity, and the anisotropic polarization due to the polarized incident light are also been discussed. Our results exhibit the great potential in the spintronic and optoelectronic applications of the materials we discussed.