Probing novel phases of matter in van der Waals magnet Fe5-xGeTe2

非技术摘要范德华材料具有垂直堆叠的原子薄层，层间结合较弱。石墨就是一个例子。它们可以被制造成二维形式，这对下一代纳米级电子学具有极大的兴趣。最近，在二维范德华材料中发现了本征磁序，这为数据存储和信息处理开辟了新的机会。范德华磁性材料在基本凝聚态物理中也很有兴趣，因为它们在晶体结构、电子态和磁序之间具有明显的相互作用，可能导致具有独特性质的新物质相。该项目将建立一种新型范德华磁性材料的结构、电子和磁性之间的关系，该材料具有高的磁转变温度和复杂的磁序。了解这些特性将有助于设计高效率的电子器件。研究目标是通过综合调查结合多种最先进的实验技术来实现的。研究活动涉及与不同学科的科学家合作，为奥本大学的研究生和本科生提供广泛的培训。将在国家实验室进行的实验将促进学生的专业发展。首席调查人员将把研究课题整合到现有的两门课程中，并将根据既定的当地推广计划继续参加K-12教育。技术摘要近年来，Fe5-xGeTe2是范德华磁性材料中的新成员，具有居里温度高、常温稳定性好等优点。值得注意的是，在这种化合物中，复杂的原子结构，加上不同的电子态和不同的自旋矩，可以强烈地影响磁序。在这个项目中，将研究晶体结构、电子态和磁序之间的相互作用，以加深对Fe5-xGeTe2中物质的新相的理解。具体地说，本项目包括三个相互交叉的目标：1)阐明晶体结构和磁性之间的关系；2)揭示电子态和磁序之间的相互作用；3)实现Fe5-xGeTe2基范德瓦尔斯异质结中磁化的电子控制。研究团队使用了一套独特的工具包，结合了非线性光学、基于同步加速器的光电子能谱/显微镜以及电磁传输技术来鉴定这种化合物的性质。我们的发现将使我们从根本上理解二维量子材料中晶格、电荷、轨道和自旋自由度之间的相互作用，并为设计自旋电子器件开辟新的途径。这笔资金促进了奥本大学的跨学科研究工作以及奥本大学和国家实验室之间的长期合作。该项目由材料研究部的电子和光子材料计划和既定的激励竞争研究计划(EPSCoR)联合资助。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。

Nontechnical abstractVan der Waals materials have atomically thin layers that are vertically stacked and have weak interlayer bonds. Graphite is one example. They can be fabricated into two-dimensional forms, which are of tremendous interest for the next generation nanometer-scale electronics. Recently, intrinsic magnetic order was demonstrated in two-dimensional van der Waals materials opening up new opportunities in data storage and information processing. Van der Waals magnetic materials are also of interest in fundamental condensed matter physics, because they possess appreciable interactions between the crystal structure, electronic states, and magnetic order that could lead to novel phases of matter with unique properties. This project will establish the relationships between the structural, electronic, and magnetic properties of a new van der Waals magnetic material with a high magnetic transition temperature and complex magnetic order. Understanding these properties will help in the design of high-efficiency electronic devices. The research goals are accomplished through comprehensive investigations combining multiple state-of-the-art experimental techniques. The research activities involve collaboration with scientists from different disciplines, which provides extensive training for graduate and undergraduate students at Auburn University. The experiments to be carried out at the national laboratories will promote the students’ professional development. The principal investigators will integrate the research topics into two existing courses and will continue to participate in the K-12 education under established local outreach programs. Technical abstractRecently, Fe5–xGeTe2 emerges as a new member in van der Waals magnetic materials with high Curie temperature and good stability in ambient conditions. Remarkably, in this compound, the complex atomic structure, together with the distinct electronic states and spin moments on the nonequivalent Fe sites can strongly impact the magnetic order. In this project, the interplay between the crystal structure, electronic states, and magnetic order will be investigated, to develop an in-depth understanding of the novel phases of matter in Fe5–xGeTe2. Specifically, this project consists of three intercrossing objectives: 1) elucidate the connection between crystal structure and magnetism; 2) reveal the interplay of electronic states and magnetic order; and 3) realize electric control of magnetization in Fe5–xGeTe2-based van der Waals heterostructures. The research team employs a unique toolset combining nonlinear optics, synchrotron-based photoemission spectroscopy/microscopy, and electro- and magnetic-transport techniques to identify the properties of this compound. Our findings will lead to the fundamental understanding of the interactions between lattice, charge, orbital, and spin degrees of freedom in two-dimensional quantum materials and open up new avenues in designing spintronic devices. This grant promotes the interdisciplinary research effort at Auburn University and the long-term collaboration between Auburn University and national laboratories.This project is jointly funded by the Electronic and Photonic Materials program in the Division of Materials Research and the Established Program to Stimulate Competitive Research (EPSCoR).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.