paper

Origin of layer number dependent linear and nonlinear optical properties of two-dimensional graphene-like SiC

arXiv:1703.07430 · doi:10.1016/j.commatsci.2018.04.058

Abstract

We theoretically discuss the physical origin of the dielectric constants [ε(ω)] and second harmonic generation coefficients [\{chi}(2)(ω)] of the ABA-stacked two-dimensional graphene-like silicon carbide (2D-SiC) with the number of layers up to 5. It is found that the intensities of the pronounced peaks of both ε(ω) and \{chi}(2)(ω) exhibit a clear layer number dependence. For the light polarization parallel to the 2DSiC plane, the monolayer SiC (ML-SiC) and multilayer SiC (MuL-SiC) have very similar pronounced peak positions of ε(ω), which are attributed to the π->π* and σ->σ* transitions. However, for the light polarization perpendicular to the 2D-SiC plane, a characteristic peak is found for the MuL-SiC at about 4.0 eV, except that the allowed π->σ* and σ->π* transition peaks are found for both ML-SiC and MuL-SiC in the high-energy region (> 8 eV). This characteristic peak is attributed to the interlayer π->π* transition which does not exist for the ML-SiC, and at this peak position, the ML-SiC has a weak dark exciton based on the mBJ calculation within the Bethe-Salpeter equation framework. For \{chi}(2)(ω), the single-particle transition channels based on the three-band terms dominate the second harmonic generation process of both ML-SiC and MuL-SiC and determine the size and sign of \{chi}(2)(ω). In the ultraviolet visible region, the purely interband motion and intraband motion of electrons competitively determine the size and sign of \{chi}(2)(ω). For the light polarization perpendicular to the 2D-SiC plane, the intraband motion of electrons modulated more dramatically the interband motion than for that parallel to the 2D-SiC plane.

34 pages, 10 figures, 3 tables

References in corpus (9)