Imaging and controlling moire interactions in two-dimensional semiconductor heterostructures

二维(2D)材料只有一个或几个原子厚。这些超薄材料展示了一系列新的电子和其他效应，这些效应应用于新技术，如高速计算、太阳能收集和基于量子的技术。在过去的十年里，人们发现了许多2D材料，包括2D金属、半导体和磁体。此外，这些2D材料可以堆叠在一起，以实现通过层之间的相互作用实现的属性。这些新特性使电子和光学设备成为可能，如晶体管、太阳能电池和激光。本研究致力于研究利用这些层间相互作用来实现新的电学和光学性质的多层2D材料样品。特别是，通过将两种不同的2D半导体组合在一起，研究小组将探索具有俘获电子的状态。这些被捕获的电子可以作为量子光源，这将有助于使量子通信设备能够安全地抵御网络攻击。这项研究与NSF关于量子飞跃的大想法是一致的：通过开发有可能实现这些新的量子信息技术的材料系统来领导下一次量子革命。此外，该项目通过拟议的研究培训和指导研究生、本科生和高中生，并通过在亚利桑那州南部的高中水平鼓励对STEM的兴趣，直接和间接地加强了STEM的劳动力。2D材料在垂直异质结构中的堆叠由于层之间的晶格失配和相对取向而导致形成长波长莫尔图案。这种莫尔图案调制了异质结构的电子和光学性质，导致电子在一层中被限制，而在另一层中被空穴限制。这些受限的间接激子被认为是量子信息科学的资源，PI将研究如何利用二维半导体异质结中的莫尔受限激子的新物理来实现具有新功能的量子器件。本项目主要研究由MoSe_2和WSe_2组成的二维半导体型过渡金属二碳化合物异质结，形成第二类异质结。本项目的研究通过全面了解扭角和层间相互作用在过渡金属二卤化物异质结构中的作用，促进了量子材料物理学的知识。具体来说，本研究有三个目的：(1)用扫描隧道显微镜成像MoSe2/WSe2异质结中的莫尔势；(2)用低温扫描近场光学显微镜直接测量空间调制的莫尔激子发射；(3)控制二维异质结中的莫尔层间激子。最后，修改层间和潜在景观之间的相互作用，允许调谐层间带隙，对捕获的莫尔激子充电，以及层间激子在莫尔势中的凝聚。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。

Two-dimensional (2D) materials are a single or few atoms thick. These ultra-thin materials exhibit a host of new electronic and other effects that have applications to new technologies, such as high speed computing, solar energy harvesting, and quantum-based technologies. Over the past decade, many 2D materials have been discovered, including 2D metals, semiconductors, and magnets. Furthermore, these 2D materials can be stacked together to realize properties that are enabled by the interactions between layers. These new properties enable electronic and optical devices, like transistors, solar cells and lasers. This research is focused on investigating multi-layer 2D material samples that use these interlayer interactions to realize new electronic and optical properties. In particular, by combining two different 2D semiconductors, the research team will explore states with trapped electrons. These trapped electrons can act as quantum light sources, which would help enable quantum communication devices that are secure against cyber-attacks. This research aligns with the NSF Big Idea of the Quantum Leap: Leading the Next Quantum Revolution by developing material systems that have the potential to enable these new quantum information technologies. Furthermore, the project strengthens the STEM workforce both directly and indirectly by training and mentoring graduate, undergraduate, and high school students through the proposed research, and by encouraging interest in STEM at the high school level in southern Arizona.The stacking of 2D materials in a vertical heterostructure leads to the formation of a long wavelength moiré pattern due to the lattice mismatch and relative orientation between the layers. This moiré pattern modulates the electronic and optical properties of the heterostructure leading to the confinement of electrons in one layer and holes in the other layer. These confined indirect excitons are known to serve as resources for quantum information science, and the PI will investigate how the novel physics of moiré confined excitons in 2D semiconductor heterostructures can be exploited to realize quantum devices with new functionalities. This project is focused on 2D semiconducting transition metal dichalcogenide heterostructures consisting of MoSe2 and WSe2 which form a type-II heterojunction. The research in this project advances knowledge of quantum materials physics by developing a comprehensive understanding of the role of twist angle and interlayer interactions in transition metal dichalcogenide heterostructures. In particular, the research has three aims: (1) Image the moiré potential in MoSe2/WSe2 heterostructures using scanning tunneling microscopy, (2) Directly measure spatially modulated moiré exciton emission using low-temperature scanning near field optical microscopy and (3) Control moiré interlayer excitons in 2D heterostructures. Lastly, modifying the interaction between layers and the potential landscape, allows for the tuning of the interlayer bandgap, the charging of trapped moiré excitons and the condensation of interlayer excitons in the moiré potential.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.