二维磁性材料CrI3、VI3及其异质结的层间磁序与拉曼光谱研究

CrI3中的磁光拉曼效应表明二维磁性材料中的拉曼散射由晶格对称性与长程磁序共同决定，为拉曼光谱直接表征本征磁性提供了可能。在块体VI3中我们也发现了层间磁序对光学声子的散射有很大影响，而薄层VI3的磁序与拉曼光谱还没有相关的报道。此外，二维材料可以通过重新堆垛形成二维范德瓦尔斯异质结，由于晶格失配或层间转角，出现Moiré超晶格，使结构或能带发生改变，从而出现非常规超导、Moiré激子、Moiré声子等新奇的现象。在二维磁性异质结中，磁近邻效应会在界面产生一个等效磁场进而影响材料的磁序与拉曼散射。本项目拟以二维磁性材料CrI3、VI3以及两者所构成的异质结为研究对象，系统研究其中的层间磁序以及层间磁序对拉曼光谱的影响，结合群论分析得出层间磁序对光学声子散射的影响规律。此外，本项目还将研究二维磁性超晶格中的层间磁序，并结合共振拉曼，探索由布里渊区折叠引入的Moiré声子的散射。

The magneto-optical Raman effects in CrI3 indicate that the Raman scattering is determined by the lattice symmetry and the long-range magnetic order in 2D magnet, which provides the possibility for the Raman spectroscopy to directly characterize the intrinsic magnetism. In bulk VI3, we also found that the magnetic order can greatly affect the scattering properties of optical phonons, however, magnetic order and Raman spectroscopy has not been reported in thin VI3. Moreover, 2D materials can form a 2D van der Waals heterojunction by restacking. Lattice mismatch or twist lead to Moiré superlattices, which changes the structure or energy bands, resulting in novel phenomena, such as unconditional superconductivity, Moiré excitons, Moiré phonons. In a 2D magnetic heterojunction, the magnetic proximity effect will generate an equivalent magnetic field at the interface and affect the magnetic order and Raman scattering of the material. In this project, we will systematically study the magnetic order and the influence of the Raman spectrum with the 2D magnet CrI3, VI3 and their heterojunction, give the general principle of influence of magnetic order on optical phonon scattering with group theory analysis. In addition, we will study the magnetic order in 2D magnet superlattice and explore the scattering of Moire phonons introduced by the Brillouin zone folding with resonance Raman spectroscopy.