Emergent electronic structure and optical properties in two-dimensional materials

作为二维材料家族的新成员，过渡金属二硫族化合物（TMDC）由于在单层极限上开始出现许多新的迷人的物理性质而引起了人们的极大兴趣，例如在brilion区边缘的直接带隙，异常强烈的光-物质相互作用，获得谷自由度以及异常强的库仑相互作用。过去，我们已经在TMDC单层中发现了一个即使在室温下也稳定的紧密结合的激子，并利用超快光成功地控制了其谷相干性。这些非凡的特性，加上材料的柔韧性，引发了人们对柔性屏幕和触摸板等设备应用的极大兴趣。***在本计划中，我们的主要重点是探索二维TMDCs中的拓扑莫尔条纹，单光子发射和稳定Floquet态等新兴现象以及相关异质结构在量子信息中的应用。我们特别感兴趣的是利用新的实验技术，如光致力显微镜、脉冲可调的超快激光和高q光学微腔，以亚衍射空间分辨率在强光场中研究TMDCs。在未来五年内，我们将研究TMDC量子点的形成机制、moir<s:1>模式对TMDC异质结构光学性质的影响以及Floquet态的热化过程等一系列悬而未决的问题。此外，我们将展示一些新的控制可能性，包括全谷伪自旋操纵、可调谐拓扑绝缘体纳米结构阵列和光诱导拓扑非平凡稳定Floquet态。一种新型的表面等离子体辅助光学近场探测器也在我们的开发计划中。***建议的研究将对物理、材料科学工程和电气工程产生重大影响。一方面，我们的研究将提供对固体拓扑效应和非平衡物理的基本理解。对TMDCs的深入了解将有助于进一步提高基于2D材料/异质结构的器件的性能。另一方面，所提出的涌现现象有望与自旋和谷自由度相结合，从而在集成平台中实现可扩展的量子信息处理。

As a new member of the two dimensional material family, the transition metal dichalcogenide (TMDC) has attracted a lot of interest because many new fascinating physical properties start to emerge at the monolayer limit, such as a direct band gap at the edge of Brillion zone, extraordinarily intense light-matter interaction, access to the valley degree of freedom, and unusually strong Coulomb interaction with reduced screening. In the past, we have discovered a tightly bound exciton stable even at room temperature in TMDC monolayer and successfully controlled its valley coherence using ultrafast light. These extraordinary properties, together with the flexible nature of the material, have triggered tremendous interest in device applications such as flexible screens and touchpads.***In this proposed program, our main focus is to explore more emergent phenomena such as the topological Moiré pattern, single photon emitter, and steady Floquet state in 2D TMDCs and related heterostructures towards quantum information applications. We are particularly interested in employing new experimental techniques such as photoinduced force microscopy, ultrafast laser with tunable pulse duration, and high-Q optical micro cavity to study TMDCs in the intense optical field with sub-diffractional spatial resolution. Within the next five years, we will investigate a series of open questions such as the formation mechanism behind the TMDC quantum dot, the impact of Moiré pattern on the optical property of TMDC heterostructures, and the thermalization process of Floquet states. Moreover, we will demonstrate some new control possibilities including the full valley pseudospin manipulation, tunable topological insulator nanostructure array, and the optical induced topologically nontrivial steady Floquet state. A new type of surface-plasmon assisted optical nearfield probe is also in our development plan.***The proposed research will have a large impact in physics, material science engineering, and electrical engineering. On the one hand, our study will provide fundamental understanding of topological effects and nonequilibrium physics in solids. The deep insights obtained for TMDCs will help further improve the performance of 2D material/heterostructure based devices. On the other hand, the proposed emergent phenomena are promising to be combined with the spin and valley degrees of freedom to enable scalable quantum information processing in an integrated platform.