Tuning the Electronic and Topological Properties of Twisted van der Waals Heterostructures

非技术摘要：在过去的几年里，在层状二维（2D）材料的密集研究工作已经导致了非凡的发现。特别感兴趣的是，由于这些系统的特定几何形状，电子结构和维度而产生的现象。此外，一个新的自由度，即从这些2D系统形成的异质结构中的晶格之间的相对扭转角，使得能够制造有效无限类的新材料，其中大部分都有待研究。该项目的研究目标是探索这些所谓的扭曲货车德瓦尔斯异质结构的量子电子特性，特别强调阐明扭曲角的调整如何影响其特性，并在此基础上设计新型量子器件。我们计划通过最简单但最有趣的vdW异质结构之一的纳米结构，传输和光谱测量来实现拟议的研究目标：通过堆叠两个石墨烯片或扭曲双层石墨烯（TwBLG）制成。这项研究活动是一个广泛整合的计划的一部分，旨在建立一个合作和开放的科学社区，指导下一代科学家，并向行业领导者和公众传播物理学。技术摘要：货车范德华异质结构构成了探索各种新的电子、相关和拓扑现象的理想平台，这是由于目前可获得的层状材料的范围很广以及在选择堆叠顺序和旋转排列方面的广泛自由度。我们计划通过在低温和可变磁场下的量子电子输运测量来研究TwBLG中的量子自旋霍尔物理和相关超导性。这项研究活动推进了我们对层间耦合和多体相关性对石墨烯基vdW异质结构的电子和拓扑行为的影响的认识，这是一个在凝聚态物理学所有领域都有分支的主题。此外，这项研究的影响远远超出了二维材料和凝聚态物理学研究：狄拉克方程（例如TwBLG）描述的系统中的相互作用，超导性和拓扑结构之间的相互作用对其他物理学科非常感兴趣，例如超冷原子物理学和高能物理学。这项研究也可能导致拓扑保护量子计算感兴趣的新型量子电路，并且在评估vdW材料作为未来纳米电子学和量子信息技术关键部件的潜力方面具有重要意义。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

Nontechnical Abstract: Over the past few years, the intensive research effort in layered 2-dimensional (2D) materials has led to an extraordinary discoveries. Of particular interest are phenomena that arise because of the particular geometry, electronic structure and dimensionality of these systems. Moreover, a new degree of freedom, namely the relative twist angle between the crystalline lattices in heterostructures formed from these 2D systems, enables the fabrication of an effectively infinite class of new materials, most of which are waiting to be investigated. The research objective of this project is to explore the quantum electronic properties of these so-called twisted van der Waals heterostructures, with especial emphasis on elucidating how tuning the twist-angle influences their properties, and build upon this understanding to engineer novel quantum devices. We plan to achieve the proposed research objective through the nanofabrication, transport and spectroscopic measurements of one of the simplest, yet most intriguing, vdW heterostructures: that made by stacking two graphene sheets, or twisted bilayer graphene (TwBLG). This research activity is part of a broadly integrated program aimed at building a collaborative and open scientific community, mentoring the next-generation of scientists, and communicating physics to industry leaders and the general public.Technical Abstract: Van der Waals heterostructures constitute ideal platforms to explore a variety of new electronic, correlated, and topological phenomena, due to the vast range of layered materials currently available and the extensive freedom in choosing the stacking order and rotational alignments. We plan to investigate quantum spin Hall physics and correlated superconductivity in TwBLG via quantum electronic transport measurements at low temperatures and variable magnetic fields. This research activity advances our knowledge of the effects of interlayer coupling and many-body correlations on the resultant electronic and topological behavior of graphene-based vdW heterostructures, a subject with ramifications in all areas of condensed matter physics. Moreover, this research has impacts well beyond two-dimensional materials and condensed matter physics research: the interplay between interactions, superconductivity, and topology in systems described by the Dirac equation (e.g. in TwBLG) is of keen interest to other physics disciplines, such as the physics of ultra-cold atoms and high energy physics. This research may also result in novel quantum circuits of interest for topologically-protected quantum computing, and is of importance in assessing the potential of vdW materials as key components of future nanoelectronics and quantum information technologies.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.