Optical Study of Electron Correlation in Graphene-Based Moire Superlattices

非技术描述：超晶格是由二维(2D)材料形成的具有不同组成的多层材料堆叠而成的堆叠，通过控制堆叠顺序、扭曲角度和电子密度的调节，在工程材料特性方面具有难以置信的灵活性。这种工程材料具有单独的2D材料所不具备的显著的电学和光学特性。该项目促进了我们对碳基材料的理解，从而使量子材料及其器件应用于量子科学和技术的新的设计原理成为可能。该项目通过提供跨学科的科学经验，帮助来自代表性不足群体的研究生和本科生弥合教科书学习和科学研究之间的差距。它激发了K-12学生对2D材料以及科学、技术、工程和数学领域的兴趣，培养了未来的劳动力。该项目还丰富了NSF资助的国家高磁场实验室用户设备的实验能力，并为广泛的量子材料研究社区的用户提供技术支持。技术描述：该项目解决了涉及少层石墨烯和六方氮化硼的莫尔超晶格中电子关联的基本问题。研究小组使用这个新的材料平台来设计和研究超导、Mott绝缘体和磁性基态--这些物理以前在高T_c超导体等传统的强相关材料中实现。本研究通过以下创新推动了二维材料领域的发展。(1)首次获得了几个石墨烯基云纹超晶格的红外光谱数据，揭示了与电子关联有关的临界能级。这些信息构成了准确的理论建模和更好地解释已发现的相关现象的基础。(2)它开发了独特的光学光谱和显微镜工具，有助于制造具有广泛可调扭角、电荷密度和能带结构的新器件结构。通过对这些设备进行电子传输测量，研究小组探索了电子关联的极限，如超导转变温度T_c。(3)系统地研究了二维材料的莫尔和非莫尔相关现象之间的联系和区别。这有助于理解莫尔超晶格在2D材料堆叠中更好地设计电子关联的确切作用。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical description:Superlattices, stacks of multiple layers of materials with different compositions, formed from two-dimensional (2D) materials host incredible flexibilities in engineering material properties through controlling the stacking order, the twist angle, and tuning of the electron density. Such engineered materials have remarkable electrical and optical properties that do not exist in individual 2D materials. This project advances our understanding of carbon-based materials, thus enabling new design principles of quantum materials and their device applications for quantum science and technology. This project helps graduate and undergraduate students from under-represented groups bridge the gap between textbook learning and scientific research by providing interdisciplinary scientific experience. It stimulates the interest of K-12 students in 2D materials and the fields of science, technology, engineering, and mathematics, training the future workforce. This project also enriches the experimental capabilities of the user facility at the NSF-funded National High Magnetic Field Laboratory and provides technical support to users in the broad quantum materials research community.Technical description:This project address fundamental questions regarding electron correlation in the moiré superlattices involving few-layer graphene and hexagonal boron nitride. The research team uses this new material platform to engineer and study superconductivity, Mott insulator, and magnetic ground states— physics that were previously realized in conventional strongly correlated materials such as high-Tc superconductors. The proposed research advances the field of 2D materials through the following innovations. (1) It generates the first infrared spectroscopy data of several graphene-based moiré superlattices and reveals critical energy scales relevant to electron correlation. Such information forms the basis of accurate theoretical modeling and better interpretation of already discovered correlation phenomena. (2) It develops unique optical spectroscopy and microscopy tools that help fabricate new device structures with widely tunable twist angle, charge density and band structures. By performing electron transport measurement on these devices, the research team explores the limit of electron correlation such as the superconducting transition temperature Tc. (3) It systematically studies the connection and difference between correlation phenomena in moiré and non-moiré systems of 2D materials. This helps understand the exact role of moiré superlattice for better engineering of electron correlation in stacks of 2D materials.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.