Weyl Semimetals in Extreme Magnetic Fields

拓扑材料的发现在凝聚态物质领域掀起了一场风暴，可能为计算、能量传输和产生以及超快速通信等新技术提供新的材料基础。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的，也许也是最令人兴奋的发展，它们既具有奇异的输运性质，又具有高度可移动的表面态。本提案的目的是找到系统的方法来识别和设计这些系统的拓扑特性，旨在回答该领域的关键问题：对称性破缺场如何影响这些特性？它们是如何与对称破序相互作用的？我们能否设计这些材料，让它们的拓扑特性凌驾于琐碎的特性之上？除了这些努力之外，PI正在开发一个雄心勃勃的媒体项目，旨在通过一系列视频教程将复杂的凝聚态思想动画化，并整合到PI的课程中。技术摘要：该提案解决了三个问题；(i)需要能够识别拓扑系统的新实验方法，（ii）除了是拓扑之外还具有对称破缺顺序的材料的缺乏，以及（iii）可以测量在这些对称破缺环境中由其类韦尔性质引起的表面和块状运输如何受到影响的实验方法。在高场下，所有的电子态都凝结成最低的朗道能级，即所谓的量子极限，材料的磁性由贝里曲率支配。PI使用这一事实来识别材料在拓扑上是平凡的，是类weyl还是类3D狄拉克。此外，本提案利用合成能力来关注复杂破碎对称附近的Weyl候选体，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，以了解复杂自旋和轨道纹理的存在如何影响表面和体态的输运。

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.