二维原子晶体共振拉曼散射的理论研究

Resonance Raman scattering (RRS) has been widely observed in two-dimensional atomic crystals (2DAC) and attracting much research attention in recent years. Resonance Raman spectra have advantages over non-resonance Raman spectra with its characteristic Raman shift and intensity depending on incident laser energy, and can unveil some essential information on structure, phononic or even electronic structure of materials. RRS is intimately relevant to the complexity of electron-photon and electron-phonon interactions. Due to the lack of quantitative analysis on the related electron-photon and electron-phonon interactions, a big controversy still exists on the assignments of normal modes and the related mechanism behind the resonance Raman spectra of 2DAC such as transition metal dichalcogenides, which hinders its applications on electronic and optoelectronic devices and therefore awaits for a systematic theoretical study. Based on ab initio calculations, this project will combine density functional (perturbation) theory, with electrodynamics and high-order perturbation theory, to construct both electron-photon and electron-phonon matrix elements and to write an original source code for systematically studying the RRS of 2DAC. Not only will this project supply an auxillary tool for characterizing electronic/phononic structure and giving a strong theoretical support to the experimental study on RRS in 2DAC, but also help unveil the physical mechanism behind the RRS process for optimizing the electronic and optoelectronic applications of new-type 2DAC.

二维原子晶体中观测到大量共振拉曼现象，引发了广泛关注。与非共振拉曼散射谱相比，共振拉曼散射谱的特征峰位和峰强会随激光能的改变而改变，能提供材料结构、声子甚至电子结构方面的深层次信息。共振拉曼散射牵涉到复杂的电-光/电-声耦合共振过程。由于缺少电-光/电-声耦合的定量化分析手段，目前对二维原子晶体（如过渡金属硫化物等）的共振拉曼散射物理机制的理解尚存在较大的争议，阻碍了其在纳米光电子器件方面的应用，亟需系统的理论研究。本项目从第一性原理计算出发，结合密度泛函(微扰)理论与量子力学高阶微扰理论，构建电-光/电-声矩阵元模型，编写相应的源程序代码，计算研究二维原子晶体的共振拉曼散射过程。本项目不仅可以丰富现有的二维原子晶体电/声子结构的表征手段，为共振拉曼的实验研究提供理论指导，而且有望阐明二维原子晶体中共振拉曼散射现象背后的物理机制，为其在纳米光电子器件的优化提供有效的理论手段。

二维原子晶体中观测到大量共振拉曼现象，引发了广泛关注。共振拉曼散射的特征峰位和峰强会随激光能的改变而改变，能提供材料声子甚至电子结构方面的深层次信息。由于缺乏系统的理论支持，二维原子晶体（如过渡金属硫化物TMDC等）中共振拉曼散射过程亟需更深入的理论研究。本项目从第一性原理计算出发，结合密度泛函理论、高阶微扰理论，编写出原创性代码，系统计算了与频移和激光能相关的共振拉曼散射强度，得到了二维原子晶体的共振拉曼散射谱。本项目初步阐明了二维原子晶体中共振拉曼散射现象背后的物理机制，澄清其中的争议；代码还在TMDC等二维原子晶体的共振拉曼散射研究中获得了应用。本研究不仅可以丰富现有的二维原子晶体电/声子结构的表征手段，为共振拉曼的实验研究提供理论指导，而且为新型二维原子晶体晶格动力学研究提供新的研究途径。