低维狄拉克费米子体系的拓扑物性和量子调控

Low dimensional Dirac fermion based materials, such as graphene, topological insulators, have been the focus of extensive research in condensed matter physics and material science for the past few years, due to their peculiar topological properties and attractive application potential in electronic devices. However, due to their weak compatibility with silicon based technology, there is still a long way to go before their applications can be realized. Two newly discovered Dirac fermion based materials, graphene sandwich and silicone, not only have the advantage of being compatible with silicon based technology, but also their spin-orbit interaction is intermediate between graphene and topological insulators, and can therefore be an important bridge for understanding the topological properties and fundamental physics of these important topological classes of materials. Here we propose to investigate the topological properties of graphene sandwich and silicene, as well as manipulation of their properties. We will grow high quality graphene sandwich and silicene, and perform a systematic study on their electronic structure and topological properties using various advanced techniques, including angle-resolved photoemission spectroscopy, scanning tunneling electron microscopy, first principle calculation etc. Moreover, we will also explore manipulation of their properties and the underlying mechanism, which will be directly relevant for their future device applications.

低维狄拉克费米子体系，如石墨烯、拓扑绝缘体等，以其独特的拓扑物性及在电子器件中的诱人的应用前景，在过去几年里迅速成长为当前凝聚态物理和材料科学的重要研究热点。然而，这些材料与硅基技术的弱兼容性使得它们的应用还有漫长的历程要走。最近发现的两种新型的狄拉克费米子体系，石墨烯三明治结构和硅烯，不仅具有与硅基技术兼容的特点，而且其自旋-耦合介于石墨烯和拓扑绝缘体之间，对理解这两些狄拉克量子材料中的拓扑物性和根本物理能起到重要的链接作用。本项目中，我们将着重研究石墨烯三明治结构和二维硅烯的拓扑性质和量子调控。我们将以高质量石墨烯三明治和硅烯等样品制备为基础，利用角分辨光电子谱和扫描隧道显微术等精密测量手段研究其电子结构，结合理论计算和微观模型，对石墨烯三明治结构和硅烯的特殊电子结构和拓扑性质进行一系列系统化的研究，并且进一步探索与其未来电子器件应用直接相关的根本物理机制及性质调控。

本项目针对新型二维材料以及狄拉克费米子体系，探索层状材料中的新奇拓扑物态、新型二维材料的制备及性质研究、范得华异质结的能带调控开展研究，并且在下述几个方面取得重要进展。（1）首次实现了破坏洛伦兹不变性的第二类外尔半金属MoTe2 （Nat. Phys. 12, 1105-1110 (2016)，文章发表至今被引用188次）和第二类狄拉克半金属PtTe2（Nat. Commun. 8, 257 (2017)）；（2）揭示了新型过渡金属硫族化合物PtSe2 单层薄膜的能隙（Nano Lett. 15, 4013 (2015)）和局域电偶极矩导致的新奇自旋结构（Nat. Commun. 8, 14216 (2017)）；（3）揭示了石墨烯/氮化硼(graphene/h-BN)范得华异质结的能带调制，解决了这个模型范德瓦尔兹异质结构中有关能带调控的若干关键问题（Nat. Phys. 12, 1111-1115 (2016)）。（4）首次制备出具有类似于准晶对称性的30度转角的非公度双层石墨烯，并且揭示了层间耦合导致的能带调控及丰富物理（PNAS 115, 6928 (2018)）。(5)制备出单层锑硒，并且通过选取合适的衬底调控原子起伏及性质(Adv. Mater. 29, 1605407 (2017); Nano Lett. 18, 2213 (2018))。.项目执行期间，项目组成员已发表高质量学术论文35篇，包括Nature子刊、PRL、PNAS等9篇。项目成员多次被邀请在国际重要学术会议做邀请报告，培养出一批具有综合国际竞争力的博士生。