Visualizing Novel Electronic Orders in Bilayer Graphene Systems

非技术摘要：量子材料在建立技术的未来方面发挥着关键作用。基于单原子厚度材料（如石墨烯）及其堆叠的发现和研究进展正在为探索电子现象创造新的竞技场，其中电子之间的相互作用可以用现代技术（如扫描隧道显微镜（STM））来控制和分析。该研究项目的重点是可视化材料中的量子现象，材料中的电子密度通过施加磁场或层之间的扭曲来控制。通过将成像电子态的力量引入这些激发材料的研究，该项目揭示了这些量子态形成的微观机制及其性质。在该项目中培训的研究生和本科生将构成学术界和工业界量子科学和技术的未来劳动力。这项研究补充了一个教育议程，继续改进普林斯顿大学本科课程“未来领导者的物理学”，介绍物理学（从基础知识到量子现象），以及对在政府和政策领域担任领导角色感兴趣的非科学专业学生。技术摘要：本计画主要研究二维材料中的电子相位，其中电子相关是由占据平坦能带的电子所引起。该研究小组利用扫描隧道显微镜（STM）的原子尺度成像和光谱学，以独特的方式探索了平带电子的各种量子现象。从这些实验中获得的信息是几乎不可能从其他类型的宏观平均方法，因此将增加一个重要的新的角度来研究电子的相互作用阶段。具有复杂对称性破缺和有序性的新量子相正在超净设备中产生，并且正在探索其形成背后的复杂相关性。奇异的电子相位与分裂的费用，可能主机非阿贝尔任意子是调查的焦点。特别是，该项目支持双层石墨烯中的分数量子霍尔相（Fractional quantum Hall phase，缩写为HHH）的检查，检查可以用STM局部探测这些状态的方法。该系统还提供了一个独特的设置，以可视化场致维格纳晶体，气泡和条纹相的电子和它们的竞争与H2OH阶段。另一个正在探索的平带系统是魔角扭曲双层石墨烯，其中STM测量用于理解对称性破缺状态的性质，这些对称性破缺状态引起在该系统中发现的相关和拓扑绝缘体。局部STM成像及其分析被用来表征对称性的破坏，并研究应变，扭转角和减去氮化硼对齐的影响。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical Abstract: Quantum materials play a key role in establishing the future of technology. The discovery of and research advances based on single-atom-thick materials, such as graphene, and their stacks is creating a new arena for exploration of electronic phenomena in which interaction between electrons can be controlled and analyzed with modern techniques such as the scanning tunneling microscopy (STM). This research project is focused on visualization of quantum phenomena in materials with density of electrons controlled by application of a magnetic field or twisting of layers relative to each other. By bringing the power of imaging electronic states to study these exciting materials, this project reveals the microscopic mechanism by which these quantum states are formed and their properties. The graduate and undergraduate students trained in this project will constitute the future workforce for quantum science and technology in academia and industry. This research is supplemented with an educational agenda, the continued improvement of a Princeton undergraduate course “Physics for Future Leaders”, that introduces physics (from basics to quantum phenomena) to non-science majors who are interested in pursuing leadership roles in government and policy arenas.Technical Abstract: This project is focused on electronic phases in novel two dimensional materials in which electronic correlation is induced by electrons occupying a flat band. The research team explores a wide range of quantum phenomena for electrons in flat bands in unique ways using atomic scale imaging and spectroscopy with the scanning tunneling microscope (STM). The information obtained from these experiments is nearly impossible to obtain from other types of macroscopically averaged methods and hence will add an important new perspective to the study of interacting phases of electrons. New quantum phases with complex broken symmetry and ordering are being created in ultra clean devices and the complex correlations underlying their formation is being explored. Exotic electronic phases with fractionalized charges that may host non-abelian anyons are the focus of investigation. In particular, the project supports examination of fractional quantum Hall phases (FQH) in bilayer graphene, examining ways in which such states can be probed locally with the STM. This system also provides a unique setting to visualize field-induced Wigner crystals, bubble and stripe phases of electrons and their competition with FQH phases. Another flat band system being explored is that of magic-angle twisted bilayer graphene in which STM measurements are used to understand the nature of broken symmetry states that give rise to correlated and topological insulators found in this system. Local STM imaging and its analysis are being used to characterize broken symmetries and to study the influence of strain, twist angle, and alignment with subtracted boron-nitride. Several new experimental techniques based on scanning tunneling microscopy is also being developed in this program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.