Discovery and Fundamental Investigation of Emergent Phenomena in Novel 2D Magnets

摘要：从指南针开始，磁性材料在技术上的重要性早就被认识到，并且是当今信息存储和许多其他标准应用的组成部分。然而，这种应用需要具有新性能的新型磁性材料。最近发现的二维（2D）磁性材料在这方面具有巨大的优势，并提供了一套现有磁性材料无法实现的独特特性。它们只有几个原子的厚度，它们很柔韧，更棒的是，它们可以像乐高积木一样堆叠在一起，形成具有新磁性的全新材料。本研究计划的目标是采用实验和理论相结合的方法来扩展二维磁体库。该项目的成果通过为数据存储、量子通信和消费电子领域的潜在应用提供新的磁性材料而造福社会。拟议的多学科研究项目还为本科生和研究生提供了一个优秀的培训平台，通过亚利桑那州立大学的SCENE项目，将K-12学生纳入积极的研究环境中，并将为现有的本科和研究生水平课程开发新的模块。技术摘要：二维（2D）范德华磁体从基础和技术角度提供了独特的机会。虽然第一个二维材料石墨烯早在2004年就被发现，但花了十多年的时间才展示出二维长程磁有序的实验证据。迄今为止，二维磁有序仅在少数材料中得到证明，居里温度（Tc）仍低于300K，这是其在应用中破坏性影响的重要考虑因素。本提案结合先进的理论和实验技术来预测、合成、表征和操纵全新类别的二维磁性材料的性质：从铁磁绝缘体，到铁磁半金属，反铁磁手性高阶拓扑绝缘体和量子反常霍尔效应绝缘体。如果成功，这些研究将为创造新的二维磁体奠定坚实的基础，将二维拓扑顺序与磁性结合起来，并在展示第一个手性高阶拓扑绝缘体方面迈出积极的一步，同时显著推进我们对二维到三维交叉极限的磁性的理解，以及压力、门控和化学取代的影响。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:Magnetic materials have long been recognized for their technological importance, beginning with the compass, and are an integral part of today’s information storage and many other standard applications. However, such applications demand new magnetic materials with new properties. The recently discovered two-dimensional (2D) magnetic materials pose an immense advantage in this regard and offer a unique set of properties that are not possible with the existing magnetic materials. They measure only a few atoms in thickness, they are flexible, and better yet they can be stacked onto each other -much like Lego bricks- to form entirely new materials with new magnetic properties. The goal of this research program is to expand the library of 2D magnets employing a combination of experimental and theoretical methods. The outcome from this project benefits society by offering new magnetic materials for potential applications in data storage, quantum communication, and consumer electronics fields. The proposed multidisciplinary research program also provides an excellent training platform for undergraduate and graduate students, involves K-12 students in active research environment through the Arizona State University SCENE program, and will enable the development of new modules for existing undergraduate and graduate level courses. Technical Abstract: Two-dimensional (2D) van der Waals magnets offer unique opportunities from a fundamental as well as a technological perspective. While the first 2D material graphene was discovered back in 2004, it took more than a decade to show experimental evidence of long-range magnetic order in 2D. To date, magnetic order in 2D has been demonstrated only in a handful of materials and Curie temperatures (Tc) remain lower than 300K which is an important consideration for their disruptive impact in applications. This proposal combines advanced theoretical and experimental techniques to predict, synthesize, characterize, and manipulate the properties of entirely new-classes of 2D magnetic materials: from ferromagnetic insulators, to ferromagnetic half-metals, antiferromagnetic chiral higher order topological insulators and quantum anomalous Hall effect insulators. If successful, these studies will lay a solid foundation to create novel 2D magnets, combine topological order with magnetism in 2D, and take aggressive steps towards demonstrating the first chiral higher order topological insulators while significantly advancing our understanding of magnetism in the 2D to 3D crossover limit, and the effects of pressure, gating, and chemical substitution.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.