Weyl Semimetals in Extreme Magnetic Fields

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Non-Technical Abstract Recent advances in the physics of material systems, often called “condensed matter” have revealed new kinds of characteristics called topological properties. Materials with certain types of topological properties can be used in manufacturing devices for quantum information technology. In this proposal, the team will investigate certain materials called Dirac and Weyl semimetals which exhibit very interesting topological properties. These materials are very challenging to synthesize, but the team has unique expertise to produce them and these will be supplied to other research groups around the world who are working to advance quantum technology. In this proposal, the materials synthesized will be studied by subjecting them to magnetic fields, to strain, and to various chemicals. Their properties will be determined through advanced techniques such as electrical transport, spectroscopy, and thermal transport measurements. The goal is to uncover new knowledge of how to tailor the topological properties of these materials so that they can be used in making devices for quantum technology. The project also includes a plan to launch an image-based book on Quantum Materials to inform the public. Graduate and undergraduate students from underrepresented groups will be recruited in this research to widen participation in this research area. Technical Abstract Three main projects are proposed that extend the idea of studying symmetry breaking fields beyond applied magnetic fields. Inspired by recent predictions that inhomogeneous strain can act as an effective magnetic field, the first project studies the effect of uni-axial strain fields on magneto-transport phenomena, in both magnetic and non-magnetic Weyl materials. The second project explores the question of the robustness of topological surface states when their protection by symmetry is compromised. In this case, the PI will study the question whether the mere proximity to a topologically non-trivial phase is sufficient to allow topological states. In the third project, the PI extends this idea further by studying competing interactions which can drive or suppress topological states, focusing in particular on how topological and emergent degrees of freedom transport charge and entropy in Kondo-lattice materials. These projects broaden the original conception of this research proposal, attacking one of the most interesting questions in the field - how is broken symmetry, and its associated correlations, intertwined with electronic topology? The project includes a plan to launch an image-based book on Quantum Materials, showcasing the recent technological advances that have allowed the visualization of the quantum nature of solids. Students from different backgrounds will be recruited to participate in the planned research project. 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.