石墨烯和拓扑绝缘体具有很多新颖的量子效应和电磁特性，在未来低能耗器件、自旋电子学和量子计算等领域具有广阔的研究和应用前景。以石墨烯、TMDC为代表的二维晶体由于电子强关联提供了极其丰富的低维体系电子、光子、声子相互作用的平台，将不同的二维材料按照某种顺序一层一层的堆栈起来形成独特的范德华异质结构，表现出更为新奇的量子调控和器件应用前景，有望为将来信息技术和能源领域带来革命性的突破。然而目前大部分用于实验研究的样品，都是利用微机械剥离的方法逐层叠加，难以实现功能异质结构的可控制备和精确定位。二维材料物性往往与杂质、缺陷和界面等密切相关，人们还未能对其界面和电子结构做系统的调控。本项目针对二维材料制备和特性研究中的关键科学问题，开展二维晶体硫化物的分子束外延生长、范德华异质结的界面、能带拓扑性质调控以及光电相互作用机理分析等研究，对于探索低维体系电子结构和性质及新型光电器件应用具有重要的意义。

Graphene and topological insulators (TIs) exhibit a variety of novel quantum effects and electromagnetic properties, which show great potential applications in low energy consumption devices, spintronics and quantum computation. At the same time, graphene and transition metal chalcogenides (TMDCs), the representative of two-dimensional (2D) atomic crystals, provide a platform for low-dimensional strong correlation systems which is extremely rich in electron, photon and phonon interaction. Isolated atomic planes can also be reassembled into unique heterostructures layer-by-layer in a precisely chosen sequence like atomic lego. Such van der Waals heterostructures have recently been fabricated and investigated, revealing unusual properties and new phenomena, exhibiting more exotic quantum manipulation and device application prospects, and is expected to bring a revolutionary breakthrough for the future information and energy technology. However, at present most of the experimental study for samples, are using the mechanical exfoliation method, which is difficult to realize the controllable preparation and precise positioning of heterostructure. The intrinsic physical properties of 2D materials is often closely associated with impurities, defects and interfaces, it is difficult to carry out a systematic study of interface engineering and optoelectronic characteristics, and to prepare controllable functional heterostructures and optoelectronic devices. This proposal aims to controllably prepare high quality 2D chalcogenides based van der Waals heterostructures with atomically sharp interface by molecular beam epitaxy (MBE) method, carry out research on the nucleation, growth kinetics and interface engineering, explore band topological properties and photoelectronic interaction mechanism of this emerging research area. With steady improvement in fabrication techniques and using graphene’s springboard, van der Waals heterostructures should develop into a large field of their own important significance for the exploration of the electronic structure of low dimensional systems and novel optoelectronic device applications.