类石墨烯层状二维材料及其异质结构的超快磁光光谱研究

Because of the quantum confinement effect, graphene-like two-dimensional (2D) materials and their van der Waals heterostructures possess a lot of novel properties beyond the conventional 3D materials, such as ultrahigh electron mobility, layer-number dependent band structure, very high exciton binding energy, strong light absorption and electron-photon coupling. Moreover, some 2D materials also have valley and topological degree of freedom which provide new approaches to control the behavior of electron. Thus, 2D materials and their heterostructures are not only wonderful objects to study the quantum effect in material, but also the promising candidate for future high performance (opto) electronics. Many characteristics of 2D materials are tightly related to magnetism, which will dramatically change under strong magnetic field, like the changing of exciton binding energy and electron-phonon coupling, topological phase transition, valley polarization, chiral anomaly and anisotropic magneto-optic/electric conductivity, which could reveal the rich and profound connotations of physics. Ultrafast magneto-optic spectroscopy is a proper and powerful method to study the magnetic effects in 2D materials, it can give us the good insights of the mechanics of carriers behaviors in them, especially for those correlated with the new quantum degrees of freedom, and at the same time, the researches can provide a guidance for the design and applications of related functional devices. However, the ultrafast magneto-optic spectroscopy study of 2D materials is almost still a void. Here, we will use the ultrafast magneto-optic spectroscopy combining with the terahertz spectroscopy to study the magneto-optic properties of 2D materials and their heterostructures, reveal the carriers dynamics and related mechanics behind.

由于量子限制效应，类石墨烯层状二维材料及其异质结构具有诸多三维体材料所不具备的优异性质。如超高电子迁移率、层数依赖的能带结构、高激子结合能、强的光吸收和电光耦合等，很多材料中还具有如能谷或拓扑结构，为电子特性调控增加了新的量子自由度，是研究材料中的量子行为，开发未来高性能电子/光电子器件的理想材料。二维材料的许多特性，尤其是新型量子自由度，与磁场有着密切的关联，磁场作用下将发生激子能量和电子—声子耦合改变、拓扑相变、谷极化、手性反常、磁光/电各向异性等现象，反映了极为深刻的物理内涵。超快磁光光谱和太赫兹谱是研究磁场下二维材料电子特性的有利手段，不仅有助于深入理解相关物理内涵，而且对其在高速光电器件、磁控器件等方面的应用具有指导意义，然而当前该方面的研究却几乎空白。本项目将利用超快磁光光谱结合太赫兹谱，针对二维材料及其异质结构磁光特性展开研究，揭示其中的载流子动力学行为和背后的物理机制。

在本项目的资助下，我们按计划通过包括超快磁光光谱、超快太赫兹谱、光电流谱等各种光学和光电测试方法对包括二维层状材料和拓扑材料等类石墨烯体系的载流子动力学，超快响应，光电响应，以及相关调控等方面开展了实验研究。两年来，研究开展顺利，已达到了研究目标成果。主要研究成果已经发表在高水平的学术杂志上, 共发表致谢和明确标注的SCI收录论文7篇，包括负责人发表在Physical Review B、2D Materials、Nanotechnology、ACS Nano、Advanced Materials上的负责人署名论文各一篇，以及未署名论文2篇发表在Nature Materials和2D Materials上。根据Web of Science统计，目前这些论文总引用已达60次。因为相关研究出国参加国际会议作报告并作墙报展示共4人次。本项目已发表的研究成果主要集中在以下三个方面：.（1）二维层状半导体材料黑磷的各向异性光学性质及超快磁光调控；.（2）狄拉克拓扑半金属砷化镉的太赫兹动力学过程；.（3）二维层状外耳拓扑半金属二碲化钼和钽铱碲的宽谱、各响异性光电响应特性。. 在此基础上团队成员在国际上首次通过中红外光验证了外尔点附近贝里曲率发散导致的显著的位移电流增强效应。.