Collaborative Research: Atomically thin topological insulators via confinement heteroepitaxy

量子计算的曙光正在迅速发展，有可能彻底改变计算领域。然而，目前基于超导体、离子或原子的量子计算机由于不完美而容易出错。解决这一重大挑战的方法是使用新的工程材料，这些材料本身就不受这些缺陷的影响。然而，关键的问题仍然是如何使材料，集成所需的苛刻性能，以实现上级性能的技术相关的方式。主要研究人员创造了一种制造超薄金属的新方法，该项目的重点是了解这些金属的微观特性，特别是铋和铅。研究人员将评估将这些材料减薄到几个原子厚的影响，以探索当它们在原子尺度上被操纵时，它们的性质如何变化。除了科学影响，这个合作项目将为代表性不足的研究生提供跨学科的研究培训，以扩大科学和工程项目的参与。该项目还将发展一个独特的工业/大学联盟，以传授工业和研究环境中安全的重要性。这不仅可以更好地培养未来的科学家在工业研究生的职业生涯，但也将提高学术界的安全准备。技术说明通过减少从3D到2D的拓扑绝缘体的维数的量子自旋霍尔绝缘体（QSHI）的创建可以提供一个独特的，强大的路线，实现拓扑超导性。该项目将研究二维铋（Bi）和铅（Pb）的原子尺度物理、化学和电子性质。铅和铋表现出非常强的自旋-轨道相互作用，以及异常稳健且易于获得的拓扑绝缘体性质，这可能使具有无耗散自旋电流的开创性电子器件的设计成为可能，并实现马约拉纳束缚态。此外，这些元素表现出非常规的超导性，并且可以与铁磁材料结合，这表明有可能创建基于Pb的拓扑超导体。研究人员通过合成通过限制异质外延（CHet）制备的这些材料的原子薄的二维形式来实现研究-这是一种新型的嵌入过程，可以稳定PI开发的3D材料的2D形式。在合成之前、期间和之后研究SiC/石墨烯界面钝化，以了解界面重建如何能够原位去除石墨烯帽以直接表征2D-Bi和Pb。 此外，去除石墨烯帽使得2D金属能够直接功能化，以探索修饰2D-Bi和Pb的表面如何改变其潜在的物理性质，包括键合和电子特性。最后，该项目正在开发一个机制的理解，如何与SiC和石墨烯的结构和界面相互作用的影响2D-Bi和2D-Pb的电子结构，并阐明它们与传统方法沉积的薄膜有何不同。该奖项反映了NSF的法定使命，并已被认为是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的支持。

Nontechnical DescriptionThe dawn of quantum computing is rapidly developing with the potential to completely transform the field of computation. However, current quantum computers based on superconductors, ions, or atoms are prone to error due to imperfections. The solution to this grand challenge is to use new, engineered materials which are inherently immune to these imperfections. However, key questions remain regarding how to make a material that integrates the demanding properties needed to achieve superior performance in a technologically relevant manner. The principal investigators have created a new method to make ultra-thin metals, and this project focuses on understanding the microscopic properties of such metals, specifically bismuth and lead. The investigators will evaluate the impact of thinning these materials down to just a few atoms thick to explore how their properties change when they are manipulated at the atomic-scale. Beyond the scientific impact, this collaborative project will provide interdisciplinary research training for underrepresented graduate students, to broaden participation in science and engineering programs. The project will also develop a unique industry/university consortium to impart the importance of safety in industrial and research settings. This will not only better train future scientists for post-graduate careers in industry, but will also improve safety preparedness in academia.Technical DescriptionThe creation of a quantum spin Hall insulator (QSHI) by reducing the dimensionality of a topological insulator from 3D to 2D could provide a unique, robust route to achieving topological superconductivity. This project will investigate the atomic-scale physical, chemical and electronic properties of 2D bismuth (Bi) and lead (Pb). Lead and bismuth exhibit very strong spin-orbit interactions, and exceptionally robust and easily accessible topological insulator properties that may enable the design of groundbreaking electronic devices with dissipationless spin currents, and the realization of Majorana bound states. Furthermore, these elements exhibit unconventional superconductivity, and could be combined with ferromagnetic materials, suggesting the possibility of creating a Pb-based topological superconductor. The investigators enable the study by synthesizing atomically thin, two-dimensional forms of these materials prepared via confinement heteroepitaxy (CHet) – a novel intercalation process that stabilizes 2D forms of 3D materials developed by the PIs. The SiC/graphene interface passivation is investigated before, during and after synthesis to understand how interface reconstruction can enable in-situ removal of the graphene cap for direct characterization access to the 2D-Bi and Pb. Additionally, removing the graphene cap enables direct functionalization of the 2D metal to explore how modifying the surfaces of 2D-Bi and Pb changes their underlying physical properties, including bonding and electronic character. Finally, the project is developing a mechanistic understanding of how the structure and interfacial interactions with SiC and graphene impact electronic structure of 2D-Bi and 2D-Pb and elucidate how they differ from thin films deposited by traditional methods.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.