CAREER: Backscattering, Confinement and Superconductivity in a Two-Dimensional Topological Insulator

非技术性：传统计算机电路的规模越来越小，正在迅速接近量子力学现象不可避免的维度。在这些规模下，理解如何利用这些量子效应来建造更强大的计算机将是至关重要的。最近，一类具有独特性质的新材料被发现，这可能对未来的信息处理技术起到重要作用。这些“拓扑绝缘体”在整体上是电绝缘的，但可以沿其边界传导电荷。这个职业项目研究的是InAs/GaSb的电子性质，这是一种二维拓扑绝缘体(2DTI)，是一种电子通过边缘沟道流动的材料。这个项目将首先阐明杂质对这些边缘通道的电阻的影响，并确定磁相互作用对电荷流的作用。此外，最近的理论工作预测，与超导体(一种没有能量损失的电荷传导的金属)接触的2D TI可以容纳Majorana态。这些新颖的量子力学状态可能会对容错量子计算产生革命性的影响。因此，本项目的第二个目标是实现和检测2D Ti超导体设备中的Majorana态。除了培训研究生和本科生在未来的科学和高科技行业的职业生涯，首席研究员(PI)将通过在当地科学博物馆和社交媒体上的活动促进对量子物理、纳米科学及其应用的更广泛的兴趣。一个主要的教育目标是通过在PI的实验室开展实习并帮助明尼苏达大学为美国原住民高中生和他们的老师组织一系列为期一周的年度夏令营来增加美国原住民学生对物理和STEM的参与。技术：该项目研究了二维拓扑绝缘体InAs/GaSb双量子阱中的后向散射、限制、拓扑超导电性和Majorana态。了解二维TI螺旋边缘模的后向散射和限制是凝聚态物理中一个重要的开放问题，对于利用自旋极化弹道输运的应用具有重要意义。研究小组使用感应量子点来模拟电荷和自旋杂质，这些杂质已经被理论上影响后向散射。研究了纳米级磁绝缘体势垒作为一种利用磁交换耦合来限制边缘模的方法。2DTIS也是实现拓扑超导和观测和操纵Majorana零能模的理想系统。据预测，Majorana模将表现出非阿贝尔、任意子交换统计，并可能在发展退相干保护的拓扑量子比特方面发挥关键作用。因此，该项目的主要目标之一是实现和检测拓扑超导和Majorana模。为此，研究小组将研究通过将InAs/GaSb与传统超导体接触而制造的混合器件。该研究项目与一项广泛的教育计划紧密结合，旨在培养研究生和本科生在科学和高科技行业取得成功，并帮助教育更广泛的公众关于纳米科学的知识。一个中心目标是增加美国原住民学生对物理和STEM学科的参与。

Non-Technical: The smaller and smaller scales of conventional computer circuits are rapidly approaching dimensions at which quantum mechanical phenomena become unavoidable. At these scales it will be paramount to understand how to harness these quantum effects in order to build more powerful computers. Recently, a new class of materials with unique properties has been discovered, which could play an important role for future information processing technologies. These "topological insulators" are electrically insulating in the bulk, but can conduct charge along their boundaries. This CAREER project studies the electronic properties of InAs/GaSb, a two-dimensional topological insulator (2D TI), a material in which electrons flow through edge channels. This project will first shed light on the effects of impurities on the electrical resistance of these edge channels and determine the role of magnetic interactions on charge flow. Furthermore, recent theoretical work has predicted that a 2D TI placed in contact with a superconductor (a metal which conducts charge without energy losses) can host Majorana states. These novel quantum mechanical states could have a transformative impact on fault-tolerant quantum computing. A second objective of this project is therefore to realize and detect Majorana states in a 2D TI-superconductor device. Beyond training graduate and undergraduate students for future careers in science and the high-technology industry, the principal investigator (PI) will promote broader interest in quantum physics, nanoscience and their applications through activities at local science museums and social media. A central educational goal is to increase the Native-American student participation in physics and STEM by launching an internship in the PI's lab and helping to organize a series of annual week-long summer camps for Native-American high-school students and their teachers at the University of Minnesota. Technical: This project studies backscattering, confinement, topological superconductivity, and Majorana states in InAs/GaSb double quantum wells, a two-dimensional topological insulator (2D TI). Understanding backscattering and confinement of 2D TI helical edge modes is a significant open problem in condensed matter physics, and is important for applications that would harness spin-polarized ballistic transport. The research team uses induced quantum dots to simulate charge and spin impurities, which have been theorized to affect backscattering. Nanoscale magnetic insulator barriers are investigated as a means of confining the edge modes using magnetic exchange coupling. 2D TIs are also ideal systems for realizing topological superconductivity and for observing and manipulating Majorana zero-energy modes. Majorana modes have been predicted to exhibit non-Abelian, anyonic exchange statistics, and could play a key role for the development of decoherence-protected topological quantum bits. One of the main objectives of this project is therefore to realize and detect topological superconductivity and Majorana modes. To this end, the research team will investigate hybrid devices made by contacting InAs/GaSb with conventional superconductors. The research project is closely integrated with an extensive educational plan to train graduate and undergraduate students for successful careers in science and the high-technology industry and help educate the broader public about nanoscience. A central goal is to increase Native-American student participation in physics and STEM disciplines.