CAREER: Study of Electronic and Magnetic Topological Phenomena in Two Dimensional Quantum Materials with Scanning Probe Microscopy

职业：利用扫描探针显微镜研究二维量子材料中的电子和磁拓扑现象

• 批准号: 2145735
• 负责人: Yongtao Cui
• 金额: $ 73.19万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-01 至 2027-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2145735&HistoricalAwards=false
• 关键词: CAREER; Study; Electronic; Magnetic; Topological

Non-technical description:The mathematical concept of topology, which studies global geometrical properties of shapes, such as the number of holes or surfaces, that remain unchanged when the objects are smoothly deformed, has been applied to understand and discover novel electronic and magnetic properties in solid state materials. This project studies two types of such phenomena in two-dimensional materials that are only a few atomic layers thick. The first is 2D materials that host topological edge conduction. In these materials, the interior of sample is insulating while electrical current can only flow along the edges. This kind of edge conduction can greatly reduce the energy loss during the current flow, therefore, it can potentially be used to develop next generation of energy efficient electronic devices. The second type of phenomena occurs in 2D magnetic materials where the local magnetic poles wind around in a swirling pattern. The winding directions can be used for information storage as their topological properties make them robust against external perturbation thus capable of retaining information for longer time. This project further integrates an education component to engage both undergraduate and high school students in multidisciplinary research in the field of quantum materials and nanotechnology. The PI will develop research modules that are suitable for students at all levels such as building demo nano characterization tools that involve both hardware design and electronics development. The demo projects provide a bridge for the students to participate in the proposed research activities. Under-represented groups will be particularly encouraged and recruited in the education programs.Technical description:Atomic layered materials provide a rich platform to study topological physics in two dimensions. This project investigates several families of novel 2D materials and their heterostructures to characterize their topological states and explore new methods to manipulate and engineer their topological properties. The first material system is the recently discovered topological magnet, MnBi2Te4, which combines magnetism and topological order in one material and is a Chern insulator in few-layer samples. The proposed research aims to characterize key properties in few-layer samples that are important for the topological order, including the topological gap and the magnetic anisotropy. The second material system is graphene based moiré heterostructures, including twisted bilayer graphene aligned on hBN and graphene interfaced with moiré heterostructures of transition metal dichalcogenides. The formation of moiré superlattice with a large periodicity is expected to modulate the Landau level structures in graphene, which could potentially be used to tune the topological states in graphene. The third material system is heterostructures of 2D magnets. The proposed research explores different material combinations to introduce strong spin orbit coupling and break inversion symmetry at the interface which could induce the Dzyaloshinskii–Moriya interaction and create skyrmions in the magnetic materials. This project employs several scanning probe microscopy techniques, including microwave impedance microscopy (MIM), electrostatic force microscopy (EFM), and magnetic force microscopy (MFM), to probe the local electronic and magnetic properties and image the topological states in real space. The local probes provide complementary information to conventional transport techniques, which can bring in new insights on topological physics in two dimensions from a different perspective. Results from this research will provide important feedback for theorists to refine model parameters and for material scientist to optimize and improve sample qualities.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.

非技术描述：拓扑学的数学概念，研究形状的全局几何特性，例如物体平滑变形时保持不变的孔或表面的数量，已应用于理解和发现新的电子和磁特性该项目研究了只有几个原子层厚的二维材料中的两种类型的现象，第一种是具有拓扑边缘传导的二维材料，在这些材料中，样品的内部是绝缘的。电流只能流动这种边缘传导可以大大减少电流流动过程中的能量损失，因此，它有可能用于开发下一代节能电子器件。第二类现象发生在局部的二维磁性材料中。磁极以漩涡形式缠绕，其拓扑特性使其能够抵抗外部扰动，从而能够更长时间地保留信息，因此缠绕方向可用于信息存储。学校学生进行多学科研究PI将开发适合各个级别学生的研究模块，例如构建涉及硬件设计和电子开发的演示纳米表征工具，为学生参与提供桥梁。拟议的研究活动将在教育计划中特别鼓励和招募。技术描述：原子层状材料为研究二维拓扑物理提供了丰富的平台。该项目研究了几种新型二维材料及其异质结构。来表征第一个材料系统是最近发现的拓扑磁体 MnBi2Te4，它将磁性和拓扑顺序结合在一种材料中，是少层样品中的陈绝缘体。表征对拓扑顺序很重要的几层样品的关键特性，包括拓扑间隙和磁各向异性。第二种材料系统是基于石墨烯的莫尔异质结构，包括排列的扭曲双层石墨烯。具有大周期性的莫尔超晶格的形成有望调节石墨烯中的朗道能级结构，这可能用于调整石墨烯中的拓扑状态。所提出的研究探索了不同的材料组合，以引入强自旋轨道耦合并打破界面处的反演对称性，从而引起Dzyaloshinskii-Moriya 相互作用并在磁性材料中产生斯格明子，该项目采用了多种扫描探针显微镜技术，包括微波阻抗显微镜 (MIM)、静电力显微镜 (EFM) 和磁力显微镜 (MFM)，以探测局部电子和磁力显微镜。磁特性并对真实空间中的拓扑状态进行成像，局部探针为传统传输技术提供了补充信息，这可以从不同的维度带来对二维拓扑物理的新见解。这项研究的结果将为理论家改进模型参数以及材料科学家优化和提高样本质量提供重要反馈。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持。审查标准。

项目成果

A Van der Waals Interface Hosting Two Groups of Magnetic Skyrmions

容纳两组磁性斯格明子的范德华接口

• DOI: 10.1002/adma.202110583
• 发表时间: 2021-12-15
• 期刊: Advanced Materials
• 影响因子: 29.4
• 作者: Yingying Wu;Brian A. Francisco;Zhijie Chen;Wei Wang;Yu Zhang;C. Wan;Xiufeng Han;H. Chi;Yasen Hou;A. Lodesani;G. Yin;Kai Liu;Yong;Kang Wang;J. Moodera
• 通讯作者: J. Moodera