Ultrasensitive Magneto-optic Imaging of Correlated Phases in Topological Materials

摘要：未来的量子计算机和量子器件可能基于材料，这些材料通过其固有特征来保护噪声，使这些器件的运行对环境扰动具有鲁棒性。然而，这些复杂材料及其相的基本物理性质才刚刚开始被揭示出来。研究小组专注于两个这样的阶段：在超导体和磁性拓扑绝缘体之间的连接处发现的手性边缘状态，以及在轻微磁化的拓扑近藤绝缘体表面上发现的手性边缘状态，两者都有望构建强大的量子计算机。在这个项目中，PI和他的团队使用了一套实验工具，包括精密磁光成像来研究这两种手性边缘状态。结果可以为拓扑保护信息处理提供知识库，可能在室温下操作。科学和教育部分为研究生和本科生提供综合和严格的科学训练，因此包括来自代表性不足群体的学生。通过外展活动，将科学的兴奋传递给少数民族和女中学生。技术摘要：手性边缘态是一种复杂的拓扑结构，在量子器件中具有潜在的应用价值。然而，它们的许多物理特性仍然未知。在这个项目中，PI和研究小组利用他们小组新开发的mK-Sagnac干涉仪显微镜对两种拓扑结构进行了成像和研究：超导体/QAH结中的量子反常霍尔（QAH）态和相关的马约拉纳手性模式，以及拓扑近道绝缘体SmB6表面的磁性手性边缘态。由于拓扑材料的表面和块体通常具有明显不同的物理性质，因此在该项目中，研究团队同时进行了Sagnac、扭矩磁强计和输运测量，以清楚地区分块体和表面状态的贡献，直到前所未有的低温。这些测量可以解析复杂的自旋和磁化结构在QAH态的边缘和体态，手性Majorana边缘模式，以及SmB6表面的磁性结构。该项目可以潜在地解决拓扑材料和器件领域的重要问题：在实际设备应用中，我们能否在接近环境温度的温度下稳定QAH效应？2. 手性马约拉纳边模式的自旋结构是什么？3. 在拓扑近藤绝缘体的表面状态中发现的量子化电导的性质是什么？科学和教育部分为研究生和本科生提供综合和严格的科学训练，因此包括来自代表性不足群体的学生。通过外展活动，将科学的兴奋传递给少数民族和女中学生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nontechnical Abstract: Future quantum computers and quantum devices will likely be based on materials that are protected from noise by their intrinsic features, making the operation of these devices robust against environmental perturbations. The fundamental physical nature of these complex materials and their phases, however, is just starting to be revealed. The research team focuses on two such phases: the chiral edge states found in the junction between a superconductor and a magnetic topological insulator, and on the surface of a slightly magnetized topological Kondo insulator, both holding promise for constructing robust quantum computers. In this project, the PI and his team use a set of experimental tools including precision magneto-optic imaging to investigate these two chiral edge states. The results could provide a knowledge base for topologically protected information processing, potentially operating at room temperature. The science and education components provide integrated and rigorous scientific training for graduate and undergraduate students, so including students from underrepresented groups. Through an outreach program, the excitement of science could be conveyed to minority and female middle school students. Technical Abstract: Chiral edge states are intricate topological structures that are potentially useful for quantum devices. However, much of their physics remains unknown. In this project, the PI and the research team utilize a newly developed mK-Sagnac interferometer-microscope in their group to image and investigate two such topological structures: the quantum anomalous Hall (QAH) state and the related Majorana chiral modes in a superconductor/QAH junction, and the magnetic chiral edge states on the surface of the topological Kondo insulator SmB6. As surface and bulk often have distinctively different physics properties in topological materials, in this project, the research team performs simultaneous Sagnac, torque magnetometry, and transport measurements to clearly distinguish the contributions from bulk and surface states down to unprecedented low temperatures. These measurements could resolve the intricate spin and magnetization structures on the edge and bulk states of QAH states, chiral Majorana edge mode, and SmB6 surface magnetic structure. This project can potentially address important questions in the field of topological materials and devices: 1. Can we stabilize QAH effect at temperatures close to ambient temperature for practical device applications? 2. What are the spin structures of the chiral Majorana edge mode? 3. What is the nature of the quantized conductance found in the surface state of topological Kondo insulator? The science and education components provide integrated and rigorous scientific training for graduate and undergraduate students, so including students from underrepresented groups. Through an outreach program, the excitement of science could be conveyed to minority and female middle school students.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.