基于掺杂，尺寸及界面效应的拓扑半金属电子能带调控研究

The discovery of topological quantum material has ignited one of the most fascinating fields of condensed matter physics. From topological insulators to semimetals, the investigation of materials with topological properties not only reveals new physical laws, but also provides more material options for future technologies. For example, topological semimetals host Dirac/Weyl points (magnetic monopoles in the momentum space) and 3D Dirac/Weyl fermions, making them important system for the study of fundamental physics; meanwhile, they are 3D analogues of graphene, hosting bulk electrons with high mobility, as well as exotic properties such as large and non-saturating magnetoresistance, making them promising candidates for next generation of electronic devices. To advance this exciting and fast developing field, we propose a program that focuses on investigating novel topological electronic structures via characterization tools such as angle resolved photoemission spectroscopy and exploring pathways (including dosing, quantum confinement, interfacial effect and etc) to tailor the electronic structure of topological semimetals. By the tailoring of the electronic structure, we hope to study the important and unresolved physical problems such as the topological phase transition; we also hope to systematically control the physical properties of topological semimetals through band tailoring for future applications.

拓扑量子材料已经成为了凝聚态物理的热点领域，从拓扑绝缘体到拓扑半金属，一大批具有拓扑性质新材料的发现展示了新的物理规律，也为未来的技术发展的提供了更多的材料选择。比如其中的拓扑半金属，它既蕴含着外尔点或者狄拉克点，以及三维外尔/狄拉克费米子这些基础物理学中重要的物理模型，又具有极高的电子迁移率，巨大及非饱和线性磁阻等优良性质，使其在应用上具有广泛的前景。本项目将在对拓扑半金属使用角分辨光电子能谱技术为主多种表征手段测量其电子结构的基础上，使用掺杂，尺度效应及异质界面效应等手段，对拓扑半金属展开电子能带调控的研究，从而研究拓扑半金属拓扑相变等尚未解决的重要物理问题；并通过对能带的调制实现对材料物理性能的调控，从而为拓扑半金属的应用打下基础.

拓扑量子材料是具有拓扑量子态的一类材料，具备对材料的缺陷或杂质等细节不敏感的特性，从而能够通过对物质能带整体把握进而调控其性能。其中的拓扑半金属体现出了体外尔/狄拉克费米子和表面态费米弧等奇异电子结构，并显现出种种优良的输运性质，使得其成为下一代电子学器件的材料候选。通过本项目，我们结合理论预言，样品合成，使用角分辨光电子能谱，隧道扫描显微镜在内的多种谱学方法对多种拓扑半金属及拓扑绝缘体进行了探索研究，并使用掺杂、插层、维度控制等手段实现能带调控进而实现对材料性能的综合性调控。项目代表性成果包括包括首次实验证实破坏时间反演对称性外尔半金属Co3Sn2S2，外尔半金属NbAs表面费米弧调控，本征磁性拓扑绝缘体MnBi2Te4探索及体系研究，新型拓扑超导材料研究，多种新型拓扑半金属研究等。本项目的成果进一步推进了拓扑量子材料领域的发展，为拓扑量子材料在拓扑量子计算及低耗散电子学器件中应用打下了基础。