Weyl Semimetals in Extreme Magnetic Fields

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

NON-TECHNICAL ABSTRACT The 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 ABSTRACT This 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.