Weyl Semimetals in Extreme Magnetic Fields

极端磁场中的外尔半金属

• 批准号: 1607753
• 负责人: James Analytis
• 金额: $ 30万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1607753&HistoricalAwards=false
• 关键词: Weyl; Semimetals; Extreme; Magnetic; Fields

NON-TECHNICAL ABSTRACTThe discovery of topological materials has taken the condensed matter community by storm, potentially providing new material foundations for novel technologies for computing, energy transmission and generation and ultra-fast communication. However, in order for the field to progress in answering fundamental questions and in finding technological applications, there is a critical need to discover new material realizations. Weyl and Dirac semi-metals are the most recent and perhaps the most exciting developments in quantum-relativistic condensed matter, harboring both exotic transport properties and highly mobile surface states. The purpose of this proposal is to find systematic methods to identify and engineer the topological properties of these systems, aiming to answer critical questions in the field: how are these properties affected by symmetry breaking fields? How do they interact with symmetry breaking order? Can we engineer the materials so that their topological properties dominate over their trivial properties? In addition to these efforts, the PI is developing an ambitious media project that seeks to animate complex condensed matter ideas in a series of video-tutorials that are integrated into the PI's courses.TECHNICAL ABSTRACTThis proposal attacks three problems; (i) the need for new experimental methods that can identify topological systems, (ii) the dearth of materials that have symmetry breaking order in addition being topological and (iii) experimental methods that can measure how surface and bulk transport arising from their Weyl-like nature are influenced in these symmetry breaking environments. At high fields all the electronic states condense into the lowest Landau level, the so-called quantum limit, and the magnetic properties of the material are dominated by the Berry curvature. The PI uses this fact to identify whether a material is topologically trivial, Weyl-like or 3D Dirac-like. Furthermore, this proposal utilizes synthesis capabilities to focus on Weyl candidates near complex broken symmetries and develops new methods to engineer their band structure. Finally, Focused Ion Beam nano-structuring techniques are utilized to shape sample geometries to understand how the transport of surface and bulk states is affected by the presence of complex spin and orbital textures.

拓扑材料的发现在凝聚态物质领域掀起了一场风暴，潜在地为计算、能量传输和发电以及超高速通信的新技术提供了新的物质基础。然而，为了使该领域在回答基本问题和寻找技术应用方面取得进展，迫切需要发现新的材料实现。Weyl和Dirac半金属是量子相对论凝聚态中最新也可能是最令人兴奋的发展，它们既具有奇异的输运性质，又具有高度流动性的表面态。这个提议的目的是找到系统的方法来识别和设计这些系统的拓扑性质，旨在回答该领域的关键问题：对称破缺场如何影响这些性质？它们是如何与对称破坏秩序相互作用的？我们能设计出这样的材料，使它们的拓扑性质主宰它们的微不足道的性质吗？除了这些努力，PI正在开发一个雄心勃勃的媒体项目，寻求在一系列视频教程中将复杂的凝聚态概念动画化，并将其整合到PI的课程中。技术摘要这项建议解决了三个问题：(I)需要能够识别拓扑系统的新实验方法，(Ii)缺乏具有对称破坏秩序的材料，以及(Iii)可以测量在这些对称破坏环境中如何影响表面和散体传输的实验方法。在高场下，所有电子态都凝聚到最低的朗道能级，也就是所谓的量子极限，材料的磁性由Berry曲率决定。PI使用这一事实来识别材质在拓扑上是微不足道的、类似Weyl的还是类似3D狄拉克的。此外，该方案利用合成能力来关注复杂破缺对称性附近的Weyl候选者，并开发了新的方法来设计它们的能带结构。最后，利用聚焦离子束纳米结构技术来塑造样品的几何形状，以了解复杂的自旋和轨道织构的存在如何影响表面态和体态的输运。