Correlated Quantum Phenomena at Superconductor/Magnetic Interfaces

摘要：近几十年来，量子材料及其相关技术一直是物理学重大突破的推动力。为了在该领域取得未来的进展，在原子水平上理解量子材料是至关重要的。该研究项目将专注于结合两个量子系统，即铁磁体（FMs）和超导体（SCs），以实现有趣的科学探索，如马约拉纳对模式和奇异自旋三重态sc的出现。这些主题将在低温下使用先进的探针进行实验研究，从而开发实用的拓扑量子比特，并为构建强大的、可扩展的量子计算机奠定基础。这项工作将影响量子材料的开发、医学、技术、金融、通信和国家安全。这个多学科研究项目的成果也有可能在高能量节约的超导自旋电子学方面取得领先发展，并推进量子信息科学和工程。在此过程中，各级博士后和学生将在量子科学/技术和材料物理的前沿进行培训。该项目将为在世界范围内开展新的理论和实验合作提供充足的机会，包括在国家实验室进行先进的原子水平界面表征。这将为学生提供机会，包括高中暑期实习生与国内和国际科学家进行科学互动，并丰富学生的教育和推广活动，包括在线和面对面的活动。技术摘要：该项目旨在研究原子分辨混合界面的量子现象。界面驱动效应是量子材料研究的关键，也是本项目研究的重点。本研究旨在通过铁磁体（FMs）和超导体（SCs）量子系统在原子水平上的结合来理解和操纵混合系统中的相关效应。该方法使研究特征界面交换相互作用成为可能，从而建立了sc中的Majorana束缚态对及其纠缠/隐形传态，以及自旋三重态Cooper配对。根据理论预测，具有大自旋轨道分裂和大间隙SC的金（111）表面态是寻找同时存在的Majorana对外观和理解定义固有行为/稳定性参数的理想平台。对于三重态对的研究，铁磁性的Ni、EuS或GdN将与Ga、Bi或sc（如Al或NbN）接近耦合，为对照研究创建模型系统。为了实现这一目标，将进行mbe生长薄膜异质结构、扫描隧道光谱和高场以及低温磁输运的研究。该项目将导致可扩展的、相干的拓扑量子比特的发展，以及超导自旋电子学理想的无耗散自旋极化源，其结果将影响量子信息科学与工程领域。项目涉及博士后和学生，在量子科学、材料物理和纳米器件技术的前沿多学科领域进行培训。为在国家实验室启动界面表征的理论和实验合作创造了机会。STEM的外展、教育和扩大参与努力解决了本科生和高中生的需求，同时促进了科学教育。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: Quantum materials and related technology have been the driving force for giant breakthroughs in physics in the recent decades. For future progress in the field it is essential to understand quantum materials at the atomic level. This research project will focus on combining two quantum systems, namely ferromagnets (FMs) and superconductors (SCs), to enable intriguing scientific inquiries such as the appearance of Majorana pair modes and exotic spin triplet SCs. These topics will be experimentally investigated at cryogenic temperatures using advanced probes, leading to developing practical topological qubits and forming the basis for building a robust, scalable quantum computer. This work will impact quantum materials development, medicine, technology, finance, communication, and national security. The outcome of this multidisciplinary research project also has the potential for leading developments in highly energy-conserving superconducting spintronics, and for advancing quantum information science and engineering. In the process, postdocs and students at all levels would be trained at the forefront of quantum science/technology and material physics. The project will open up ample opportunities for initiating new theoretical and experimental collaborations worldwide, including advanced atomic level interface characterization at national laboratories. This will provide opportunities to the students including high school summer interns for scientific interaction with national and international scientists, and for enriching students' educational and outreach activities, both online and in-person.Technical Abstract: The project aims at investigating quantum phenomena at atomically resolved hybrid interfaces. Interface driven effects are pivotal in quantum materials study, a focus of this project. This study intends to understand and manipulate correlated effects in hybrid system by combining the quantum systems - ferromagnets (FMs) and superconductors (SCs) at the atomic level. This approach enables the study of signature interfacial exchange interaction, leading to establishing the Majorana bound state pair and their entanglement/teleportation, as well as the spin triplet Cooper pairing in SCs. Following the theoretical prediction, gold (111) surface state with its large spin orbit splitting in conjunction with a large gap SC, is an ideal platform for seeking the simultaneous Majorana pair appearance and understanding the parameters that define the intrinsic behavior/stability. For the triplet pair study the ferromagnetic Ni, EuS or GdN would be proximity-coupled to Ga, Bi or SCs such as Al or NbN, creating model systems for controlled study. To reach the goal, MBE-grown thin film heterostructures, scanning tunneling spectroscopy and high field as well as cryogenic magneto-transport studies would be carried out. The project will lead to a scalable, coherent topological qubit development, and an ideal dissipationless spin polarized source for superconducting spintronics, and the results will impact the field of quantum information science and engineering. Project involves postdocs and students to be trained in multidisciplinary areas at the forefront of quantum science, material physics and nanodevice technology. Opportunities are created for initiating theoretical and experimental collaborations worldwide in interface characterization at national laboratories. Outreach, education and broadening participation efforts in STEM address the needs of undergraduates and high school students, while promoting scientific education.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.