Discovery and Control of Skyrmions in 2D van der Waals Magnets

非技术摘要工程磁性材料在数据存储(硬盘驱动器、唱片)、声音工程(电吉他、扬声器)、交通运输(子弹头列车、悬挂)和许多其他领域取得了突破性的发现。这个由联邦政府资助的项目旨在将传统的磁性引入纳米尺度，以实现原子尺度的磁场模式，类似于刺猬的尖峰，称为Skyrmions。Skyrmion形成在逻辑和信息存储方面提供了传统磁性材料不可能实现的新功能。通过这笔资金，该团队的目标是实现原子薄材料中的Skyrmions，了解它们的磁性行为，并操纵它们的性质。同时，该项目旨在发现新型磁性材料和技术，这些材料和技术将提高美国在全球范围内的军事和经济竞争力，并为实现量子存储器、逻辑和通信设备的高性能和下一代应用开辟道路。该项目的直接社会影响将通过在积极的研究环境中对高中、本科生和研究生的培训以及向学生介绍STEM领域和材料科学的K-12外联努力来体现。技术摘要磁性Skyrmions是一种受拓扑保护的纳米尺寸的自旋织构，具有令人兴奋的量子特性，适用于信息和神经启发技术。到目前为止，实验上已知的天离子平台仅限于块状晶体和金属多层膜。这个项目的最终目标是在实验上稳定二维(2D)和范德华层状材料中的Skyrmions，并研究由降维引起的浮现性质。该项目将以过渡金属二卤化物及其莫尔超晶格为平台，结合理论和实验研究，探索实现Skyrmion的三种不同机制：1)铁磁单分子膜中的反转对称破缺，2)铁磁单分子膜中的可调电场，3)同双分子膜中的双纵行波。该项目将利用磁光克尔、洛伦茨显微镜和钻石-NV原子力显微镜技术来从实验上了解它们的磁性。密度泛函和蒙特卡罗研究将为全面理解这些2D天离子平台提供理论上的见解。这个项目的结果将通过确定在单层和几层极限下哪些标志特征对于天空米子的形成是重要的，从而填补该领域的一个巨大的基础知识空白。该项目的社会影响将通过对记忆、逻辑和通信设备的新应用以及尖端的K-12和一般公众推广活动来体现。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-technical AbstractEngineering magnetic materials has led to ground-breaking discoveries in data storage (hard-drives, records), sound engineering (electric guitars, speakers), transportation (bullet trains, suspensions), and many others. This federally funded project aims to take traditional magnetism into nanometric dimensions to realize atomic-scale magnetic patterns resembling a hedgehog’s spikes, called skyrmions. Skyrmion formation offers new functionalities in logic and information storage that are not possible in traditional magnetic materials. Through this funding, the team aims to realize skyrmions in atomically thin materials, understand their magnetic behavior, and manipulate their properties. While doing so, the project aims to discover novel classes of magnetic materials and technologies that will increase the U.S military and economic competitiveness at a global scale and open ways to realize high-performance and next-generation applications towards quantum memory, logic, and communication devices. The immediate societal impacts of the project will manifest through high-school, undergraduate and graduate student training in an active research environment as well as K-12 outreach efforts to introduce students to STEM fields and materials science. Technical AbstractMagnetic skyrmions are topologically protected nanometric size spin textures with exciting quantum properties towards information and neuro-inspired technologies. To date, the experimentally known skyrmionic platforms are restricted to bulk crystals and metallic multilayer films. The ultimate goal of this project is to experimentally stabilize skyrmions in two-dimensional (2D) and van der Waals layered materials and investigate emergent properties arising from reduced dimensions. The project will use transition metal dihalide monolayers and their moiré superlattices as a platform and it will combine theoretical and experimental studies to explore three different mechanisms for skyrmion realization: 1) inversion symmetry breaking in ferromagnetic monolayers, 2) tunable electric fields in ferromagnetic monolayers, 3) twistronics in homobilayers. The project will utilize magneto-optical Kerr, Lorentz microscopy, and diamond-NV atomic force microscope techniques to experimentally understand their magnetic properties. Density functional and Monte-Carlo studies will offer theoretical insights for complete understanding of these 2D skyrmionic platforms. The results from this project will fill a large fundamental knowledge gap in the field by establishing what hallmark characteristics are important for skyrmion formation in the monolayer and few-layer limit. Societal impacts of the project will manifest through new applications towards memory, logic, and communication devices and through cutting edge K-12 and general public outreach activities.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.