拓扑半金属及拓扑边缘态光电响应及热电子输运研究

Topological semimetals are the extension of the concept of wave function topology in semimetal systems. The study of the singularity caused by the topological properties of the wave function in the topological semimetal is of great significance for understanding the effect of topological properties on the properties of the material. In addition, the zero-bandgap characteristic of semimetal makes it very suitable for optoelectronic applications, the research on the photoelectric response of topological semimetal is the basis of optoelectronic application using this emerging material system..The aim of this project is to study the photoelectric properties of topological semimetals represented by Weyl semimetals and their edge states, and to explore the singular photoelectric response behavior caused by the topology of materials. In this project, we will study the photoelectric properties of topological semimetals, such as type II Weyl Semimetal MoTe2 and WTe2, and their topological edge states by using scanning photocurrent spectroscopy and time-resolved photocurrent spectroscopy. The research will focus on the singular photoelectric response caused by wave function topology and topological edge. The research explores the hot carriers transport rules after photo excitation in topological semimetal and the method of enhancing the efficiency of hot electrons generation by introducing topological edge states or plasmons. This project will lay the foundation for the application of topological semimetals in optoelectronics.

拓扑半金属是波函数拓扑概念在半金属体系的延伸，对拓扑半金属中由波函数拓扑性质引起的奇异特性的研究，对于理解拓扑性质对材料物性的影响具有重要意义。此外，拓扑半金属的零带隙、高迁移率等特性使得其非常适合光电方面的应用，对拓扑半金属光电响应性质的研究，为探索这一新兴材料体系在光电方面的应用奠定基础。.本项目旨在研究以Weyl半金属为代表的拓扑半金属材料及其边缘态的光电响应性质，探索由材料拓扑性质所引起的奇异的光电响应行为。研究将以MoTe2 及WTe2等第二类Weyl半金属为研究体系，采用微区扫描光电流谱、时间分辨光电流谱等实验手段，对拓扑半金属及其拓扑边缘态的光电响应性质等进行系统研究，着重探究材料拓扑性及拓扑边缘态所引起的奇异的光电响应行为。探索拓扑半金属在光激发后的热载流子输运规律以及利用拓扑边缘态增强热电子的产生效率的方法，为拓扑半金属材料在光电探测等光电子方面的应用奠定基础。

本项目旨在研究拓扑半金属材料、拓扑绝缘体材料两大类材料的光电响应性质，以及这两类材料中拓扑边缘态对光电响应性质的影响。项目执行过程中，我们对外尔半金属材料WTe2、TaIrTe4，节线半金属材料Nb3SiTe6，拓扑绝缘体材料MnBi2Te4及Bi4Br4的光电响应及热载流子输运性质进行了研究并取得了很好的研究结果。我们发现了Weyl半金属材料WTe2边界位置由于对称性破缺而导致的光电响应并给出了系统研究结果并分析了光电流产生的机制，我们同时还指出了拓扑边缘态在光电响应中可能起到的作用，为后续理论及实验工作奠定了基础。另外，我们发现节线半金属材料Nb3SiTe6中存在较高的热电系数，热电输运结果给出了热电系数在不同条件下的具体数值，同时光电响应测试结果也表明光致热电效应是该材料中光电响应的主要机制。我们的研究成果加深了对拓扑材料光电响应性质的认识和理解，为基于拓扑材料的新型光电器件提供物理基础。另外，研究结果在光电探测领域具有潜在的应用价值。