Postdoctoral Fellowship: MPS-Ascend: Moire Engineering in van der Waals Heterostructures

由单个原子层制成的半导体与块状晶体有很大的不同。例如，二维（2D）材料结合了高机械强度和各种可调电性能。人们还可以通过将不同的晶体堆叠在一起来制造具有独特功能的异质结构。控制材料性能的一种很有前途的方法是改变两个原子薄层的相对方向，以创建纳米级的莫尔条纹。这种波纹结构有潜力为节能计算和其他应用提供新型设备。目前，制造和控制莫尔干涉图案的唯一方法是物理堆叠和旋转单个层。本项目将探索通过施加机械力（应变）来控制波纹格。应变工程与任何类型的二维异质结构兼容，因此可以实现广泛的新型器件。考虑到人工智能和数据中心需要大量的能源，这项工作可能会影响全球的日常技术。PI将通过指导本科生并让他们参与研究来扩大这项工作的影响。她还将让当地的高中生参与实验工作，激励新一代的科学家和工程师。这项MPS-Ascend研究项目的目标是全面了解扭曲双层石墨烯中有关异应变（大小和方向）和扭转角偏差的相关电子态。这项系统的研究将为如何可靠地获取和控制扭曲双层石墨烯异质结构中的超导性等相关电子现象提供模板。此外，我们将研究如何在异应变非扭曲双层石墨烯结构中创建和控制莫尔干涉图案，然后再次系统地研究与异应变应用相关的电子特性。在通过异质应变非扭曲双层成功获得摩尔异质干涉后，这将允许以可扩展，可控的方式获得摩尔异质结构，可以与工业纳米制造工艺集成。由于这种方法是可扩展的，并且与任何基于范德华的异质结构兼容，因此这项工作可以扩展到控制由莫尔条纹干涉模式决定的更多特性，并使器件结构能够利用莫尔条纹超晶格承载的奇异特性。该奖项反映了美国国家科学基金会的法定使命，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 DescriptionSemiconductors made from a single atomic layer profoundly differ from bulk crystals. For example, two-dimensional (2D) materials combine high mechanical strength and an assortment of tunable electrical properties. One can also make heterostructures with unique functionality by stacking different crystals together. A promising way to control material properties is to vary the relative orientation of two atomically thin layers to create a nanoscale moiré pattern. Such moiré structures have the potential to enable new classes of devices for energy efficient computing and other applications. Currently, the only way to make and control moiré interference patterns is by physically stacking and rotating individual layers. This project will explore the control of moiré lattices by applying mechanical force (strain). Strain engineering is compatible with any type of 2D heterostructure, and thus could enable a wide range of novel devices. Given the enormous amount of energy required for artificial intelligence and data centers, this work could impact everyday technology across the globe. The PI will amplify impact of this work through by mentoring undergraduate students and involving them in research. She will also involve local high school students with hands on experimental work, inspiring a new generation of scientists and engineers.Technical DescriptionThe goal of this MPS-Ascend research project is to obtain a comprehensive understanding of correlated electronic states available in twisted bilayer graphene with respect to both heterostrain (magnitude and direction) and twist angle biases. This systematic study will provide the community a template on how to reliably access and control correlated electron phenomena such as superconductivity in twisted bilayer graphene heterostructures. In addition, we will investigate how to create and control moiré interference patterns in heterostrained non-twisted bilayer graphene structures, then again systematically examine correlated electronic properties with respect to heterostrain application alone. Upon successfully obtaining a moiré interference through heterostrained non-twisted bilayers, this will allow moiré heterostructures to be obtained in a scalable, controllable fashion that can be integrated with industrial nanofabrication processes. As this method is scalable and compatible with any van der Waals based heterostructure, the work can be extended to control more properties dictated by moiré interference patterns and enable device structures that leverage the exotic properties hosted by moiré superlattices.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.