类石墨烯结构二维层状碳化硅的非线性二次谐波特性的第一性原理研究

二维层状碳化硅（two-dimensional layered silicon carbide，2d-SiC）是一种类石墨烯结构的半导体，在非线性光学频率转换上具有潜在的应用.本文基于第一性原理高精度全电子势线性缀加平面波结合态求和方法研究了层叠和拉伸下类石墨烯2d-SiC结构的非线性二次谐波系数.非线性过程物理源分析表明，三带项构成的单粒子跃迁过程是2d-SiC结构的二次谐波过程的主要微观跃迁机制，电子的带间运动显著受到带内运动的调谐，π电子离域带对非线性过程有重要贡献.理论上给出了2d-SiC结构的二次谐波系数的角度依赖，为实验研究提供理论参考.拉伸可导致不同频率的二次谐波增强.

First-principles study of stacking effect on second harmonic generation of graphene-like two-dimensional silicon carbide

Two-dimensional layered silicon carbide (2d-SiC), a semiconductor with graphene-like structure, has potential applications in nonlinear optical frequency conversion. The effect of stacking and strain on the nonlinear second harmonic generation (SHG) coefficient are studied by using the first-principles calculation of the all-electron full-potential linearized augmented-plane wave combined with the sum-over-states method. The analysis of physical origin of the SHG process shows that the single-particle transition channel formed by three bands dominates the SHG process of 2d-SiC. The interband motion of electrons is significantly tuned by the intraband motion. The angle dependence of the SHG coefficient of 2d-SiC is given as a reference for future experiments. A tunable SHG enhancement could be obtained by straining 2d-SiC.