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

非技术：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。在这样的尺度下，理解如何利用这些量子效应来制造更强大的计算机将是至关重要的。最近，一类具有独特性能的新材料被发现，它可能在未来的信息处理技术中发挥重要作用。这些“拓扑绝缘体”在整体上是电绝缘的，但可以沿着它们的边界传导电荷。本CAREER项目研究InAs/GaSb的电子特性，InAs/GaSb是一种二维拓扑绝缘体（2D TI），电子在其中通过边缘通道流动。该项目将首先阐明杂质对这些边缘通道电阻的影响，并确定磁相互作用对电荷流动的作用。此外，最近的理论工作预测，与超导体（一种传导电荷而没有能量损失的金属）接触的二维TI可以拥有马约拉纳态。这些新颖的量子力学状态可能对容错量子计算产生变革性影响。因此，该项目的第二个目标是在二维ti超导体器件中实现和检测马约拉纳态。除了培养研究生和本科生在科学和高科技行业的未来职业，首席研究员（PI）将通过当地科学博物馆和社交媒体的活动促进对量子物理学、纳米科学及其应用的更广泛的兴趣。一个核心的教育目标是通过在PI的实验室开展实习，并帮助在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：本项目研究InAs/GaSb双量子阱中二维拓扑绝缘体（2D TI）的后向散射、约束、拓扑超导和马约拉纳态。了解二维TI螺旋边缘模式的后向散射和约束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非常重要。研究小组使用诱导量子点来模拟电荷和自旋杂质，这些杂质在理论上会影响后向散射。研究了利用磁交换耦合限制纳米级磁绝缘子边缘模式的方法。二维ti也是实现拓扑超导和观测和操纵马约拉纳零能模式的理想系统。据预测，马约拉纳模式表现出非阿贝尔、任意子交换统计量，并可能在退相干保护拓扑量子比特的发展中发挥关键作用。因此，该项目的主要目标之一是实现和检测拓扑超导性和马约拉纳模式。为此，研究小组将研究通过将InAs/GaSb与传统超导体接触制成的混合器件。该研究项目与一项广泛的教育计划紧密结合，该计划旨在培养研究生和本科生在科学和高科技行业取得成功的职业生涯，并帮助向更广泛的公众普及纳米科学。其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.