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

职业：二维拓扑绝缘体中的反向散射、限制和超导性

• 批准号: 1554609
• 负责人: Vlad Pribiag
• 金额: $ 64.29万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2022-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1554609&HistoricalAwards=false
• 关键词: CAREER; Backscattering; Confinement; Superconductivity; Two

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.

非技术性：传统计算机电路的尺寸越来越小，正在迅速接近量子力学现象变得不可避免的尺寸。在这些规模上，了解如何利用这些量子效应来构建更强大的计算机至关重要。最近，发现了一类具有独特性能的新型材料，它可以在未来的信息处理技术中发挥重要作用。这些“拓扑绝缘体”整体上是电绝缘的，但可以沿其边界传导电荷。该职业项目研究 InAs/GaSb 的电子特性，InAs/GaSb 是一种二维拓扑绝缘体 (2D TI)，是一种电子流过边缘通道的材料。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的作用。此外，最近的理论工作预测，与超导体（一种在没有能量损失的情况下传导电荷的金属）接触的 2D TI 可以呈现马约拉纳态。这些新颖的量子力学状态可能会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 2D TI 超导器件中实现并检测马约拉纳态。除了为研究生和本科生提供未来在科学和高科技行业的职业培训之外，首席研究员 (PI) 还将通过当地科学博物馆和社交媒体的活动，促进人们对量子物理、纳米科学及其应用的更广泛兴趣。中心教育目标是通过在 PI 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及其老师组织一系列为期一周的年度夏令营，提高美国原住民学生对物理和 STEM 的参与度。技术：该项目研究 InAs/GaSb 双量子阱（一种二维拓扑绝缘体 (2D TI)）中的反向散射、限制、拓扑超导性和马约拉纳态。了解 2D TI 螺旋边缘模式的反向散射和限制是凝聚态物理中的一个重要的开放性问题，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，理论上这些杂质会影响反向散射。研究了纳米级磁绝缘体势垒作为使用磁交换耦合限制边缘模式的一种手段。二维 TI 也是实现拓扑超导以及观察和操纵马约拉纳零能量模式的理想系统。据预测，马约拉纳模式将表现出非阿贝尔、任意子交换统计数据，并且可能在退相干保护拓扑量子位的开发中发挥关键作用。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。该研究项目与广泛的教育计划紧密结合，旨在培训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，并帮助教育更广泛的公众有关纳米科学的知识。中心目标是增加美国原住民学生对物理和 STEM 学科的参与。