MRI: Acquisition of A Low-Temperature Scanning Tunneling Microscope For Advanced Surface Analysis

摘要美国卡内基梅隆大学的五位教授将通过美国国家科学基金会核磁共振项目获得一台低温扫描隧道显微镜（LT-STM）。这种仪器可以在低温和强磁场下绘制表面上的原子排列图。研究将集中在“二维（2D）材料”上，即只有一层原子厚度的材料。在这种材料中，电子被限制在单原子层内运动，因此它们获得了一些常规三维材料所没有的新特性。此外，在提议的工作中，不同类型的2D层将堆叠在另一个层的顶部。这种二维材料的组合所具有的特性，又一次不同于常规的三维材料。例如，人们发现电子在二维材料中的移动速度比在三维材料中的移动速度快得多，这使得制造新型电子设备成为可能（这对速度更快、功耗更低的计算机很有用）。此外，二维电子的磁性与三维电子不同，这也为新型计算设备提供了潜力。LT-STM不仅会对卡内基梅隆大学的研究人员产生影响，而且会对“匹兹堡量子研究所”产生更广泛的影响，该研究所包括来自匹兹堡大学、CMU和Dusquesne大学的约50名教职员工。拟议的LT-STM将作为本研究所成员开展的研究项目的有力表征工具。卡内基梅隆大学（CMU）的五名研究人员提出了一种低温扫描隧道显微镜（LT-STM），包括磁场能力。二维（2D）材料和异质结构将被研究。这种二维材料只有一个或几个原子层厚，是通过从大块晶体上“剥离”而形成的，即从大块晶体上剥离一个或几个原子层，并将这些原子层沉积在合适的惰性衬底上。这样的二维层表现出许多奇异的特性，包括无质量费米子、拓扑保护态、超导性和铁磁相，所有这些都将在LT-STM中进行探测。另外，通过将一个原子层转移到另一个原子层上，将形成垂直异质结构；CMU拥有最先进的制造设备。材料的性质可以在这种异质结构中控制，因为一层靠近另一层的存在会产生不同于单个层的集体行为。所有的研究人员都积极指导研究生和本科生的研究，而拟议的LT-STM仪器将大大加强这些活动。此外，该设施将影响目前在CMU进行的与研究人员实验工作相关的理论研究。该仪器还有望对CMU的“二维材料和节能计算设备中心”产生重大影响，其中四个pi是该中心的成员。已经为LT-STM制定了一项操作计划，将允许外部用户使用它。其中四名研究人员是“匹兹堡量子研究所”的成员，该研究所包括来自匹兹堡大学、CMU和Dusquesne大学的约50名教职员工。拟议的LT-STM将作为本研究所成员开展的研究项目的有力表征工具。

Non-technical AbstractFive professors at Carnegie Mellon University will acquire a low-temperature scanning tunneling microscope (LT-STM), through the NSF MRI program. This instrument permits the mapping of atomic arrangements on surfaces, at low temperatures and under high magnetic fields. Studies will focus on "two-dimensional (2D) materials", that is, materials that are only one layer of atoms thick. In such materials, electrons are confined to move within the single atomic layer, and they thereby acquire certain novel properties that do not occur for regular, three-dimensional materials. Additionally, in the proposed work, different types of 2D layers will be stacked on top of another. Such combinations of 2D materials possess properties that, again, are unlike any found in regular, three-dimensional materials. For example, electrons are found to move much faster in 2D materials than in 3D materials, permitting the fabrication of novel types of electronic devices (useful for computers that are faster and require less power). Additionally, the magnetic properties of electrons in 2D are unlike anything that occurs in 3D, which also has potential for new types of computing devices. The LT-STM will have impact not only for the researchers at Carnegie Mellon University, but also more broadly for the "Pittsburgh Quantum Institute", which includes about 50 faculty from University of Pittsburgh, CMU, and Dusquesne University. The proposed LT-STM will serve as a powerful characterization tool for research projects undertaken by members of this Institute. Technical AbstractFive investigators from Carnegie Mellon University (CMU) propose to acquire a low-temperature scanning tunneling microscope (LT-STM), including magnetic field capability. Two-dimensional (2D) materials and heterostructures will be studied. The 2D materials, which are only one or a few atomic layers thick, are formed by "exfoliation" from bulk crystals, that is, peeling off one or a few atomic layers from a bulk crystal and depositing those layer(s) on a suitable inert substrate. Such 2D layers exhibit a host of exotic properties including massless fermions, topologically protected states, superconductivity, and ferromagnetic phases, all of which will be probed in the LT-STM. Additionally vertical heterostructures will be formed by transferring one atomic layer atop the other; a state-of-the-art facility for performing such fabrication exists at CMU. Properties of the materials can be controlled in such heterostructures, since the presence of one layer in proximity to another yields collective behavior that differs from that of the individual layers. All of the investigators are active in directing graduate and undergraduate research, and the proposed LT-STM instrument will significantly enhance those activities. Additionally, the facility will impact theoretical studies presently performed at CMU related to the experimental work of the investigators. The instrument is also expected to have significant impact on the "Center for 2D Materials and Devices for Energy-Efficient Computing" at CMU, which four of the PIs are members of. An operating plan for the LT-STM has been formulated that will permit external users to have access to it. Four of the investigators are members of the "Pittsburgh Quantum Institute", which includes about 50 faculty from University of Pittsburgh, CMU, and Dusquesne University. The proposed LT-STM will serve as a powerful characterization tool for research projects undertaken by members of this Institute.