Exploring Emergent Magnetic Topological States in Three-Dimensional Magnetic Topological Insulator Multilayers

基于量子的技术有望在计算、传感、通信和计量方面取得革命性的进步，但成功取决于创造一个材料平台，在这个平台上，量子态可以对环境退相干产生鲁棒性，同时又可以对控制和测量进行修正。基于量子技术的一个有吸引力的方案涉及一类称为磁性拓扑绝缘体的材料，其中导电电子可以被限制在样品的边缘或表面，并且可以无阻力地流动。在本项目中，课题组基于LEGO设计方案，以磁性拓扑绝缘体为主要构件，构建了多个多层异质结构，并探索了其中的突现量子现象。这个项目的成功将促进对磁性和拓扑之间相互作用的认识。此外，这项研究加强了宾夕法尼亚州立大学的物质努力。该研究团队积极将研究生和本科教育纳入该项目，特别注重提高代表性不足的少数民族的参与度，并针对州立大学地区学区的K-12学生和教师开展外展活动。技术摘要目前对磁性拓扑态的研究主要集中在量子反常霍尔态和磁性Weyl半金属。由于缺乏合适的磁性材料平台，其他磁性拓扑相，包括轴子绝缘子、三维量子反常霍尔态和高阶磁性拓扑绝缘子的实现仍然受到限制。该项目的目标是使用磁性掺杂和未掺杂的拓扑绝缘体和正常绝缘体层作为构建多层异质结构的基石，作为创建和操纵这些磁性拓扑状态的高度可调平台。这些磁性拓扑绝缘体多层异质结构的物理性质是通过结合先进的实验探针，如电输运，扫描隧道显微镜和光谱学，角度分辨光谱学，复杂的理论建模和材料模拟来探索的。磁性拓扑状态在磁性拓扑绝缘体多层异质结构中的实现，为高效节能电子和自旋电子器件的研制铺平了道路。该研究也为量子异常霍尔绝缘子和轴子绝缘子在量子信息技术中实现变革性电磁应用提供了科学基础。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。

Non-technical abstractQuantum-based technologies promise revolutionary advances in computing, sensing, communication, and metrology, but success hinges on the creation of a material platform in which a quantum state can be made robust against environmental decoherence yet simultaneously be amendable to control and measurement. An attractive scheme towards quantum-based technologies involves a class of materials called magnetic topological insulators where the conducting electrons can be confined to the edges or surfaces of the sample and flow without resistance. In this project, based on a LEGO design scheme, the research team employs magnetic topological insulators as primary building blocks to construct a number of multilayer heterostructures and explores the emergent quantum phenomena therein. The success of this project will advance knowledge of the interplay between magnetism and topology. Moreover, this research enhances the material efforts at Penn State. This research team actively integrates graduate and undergraduate education into the project, with a particular focus on increasing participation among underrepresented minorities, and also develops outreach activities that target K-12 students and teachers from the State College Area School District.Technical AbstractCurrent research on magnetic topological states focuses on the quantum anomalous Hall state and magnetic Weyl semimetals. The realization of other magnetic topological phases, including axion insulators, the three-dimensional quantum anomalous Hall state, and higher-order magnetic topological insulators, is still limited due to the lack of suitable magnetic material platforms. The goal of this project is to use magnetically doped and undoped topological insulators and normal insulator layers as building blocks to construct multilayer heterostructures as a highly tunable platform for creating and manipulating these magnetic topological states. The physical properties of these magnetic topological insulator multilayer heterostructures are explored by combining advanced experimental probes, such as electrical transport, scanning tunneling microscopy and spectroscopy, and angle-resolved photoemission spectroscopy, with sophisticated theoretical modeling and material simulations. The realization of magnetic topological states in magnetic topological insulator multilayer heterostructures may pave the way for energy-efficient electronic and spintronic devices. This study also provides the scientific foundation in quantum anomalous Hall and axion insulators to achieve transformative electromagnetic applications in quantum information technology.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.