Domain Dynamics and Ultrafast Switching in Magnetic Weyl Semimetals

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

NON-TECHNICAL SUMMARY Electronic materials are traditionally characterized as metals or insulators based upon their ability to conduct electricity. Lying between these are semiconductors, insulating when pure but conductive when electrically or chemically doped. Researchers have uncovered whole new classes of materials, "topological materials," that defy this established paradigm. This project supports experimental research and education in magnetic topological metals, materials with unique properties and potential for use in advanced technologies. For example, magnetic topological metals host different memory states with a fictitious magnetic field pointing in different directions. Such states can be switched at fast than GHz frequencies and could be used as the basis for a new type of memory logic. The investigators will use light to study the properties of magnetic topological metals as a function of time and position, and control ultrafast switching between states. This project will help to establish a fundamental understanding of these materials and potentially enable their practical use in future nanoelectronics and quantum computing. Educational work fostered by this project includes new outreach methods that will introduce quantum materials to STEM students and the general public. First-generation college students will be involved to give them a sense of modern research in quantum materials. TECHNICAL SUMMARY The discovery of Weyl semimetals is a breakthrough in topological materials because unlike the quantum Hall effect and topological insulators which need a bulk gap to protect their novel properties, Weyl semimetals do not. Since the discoveries of magnetic Weyl semimetals such as Co3Sn2S2, their characterization has been limited to surface-sensitive band structure measurements and transport measurements. How the Berry curvature (magnetic field in the momentum space) manifest in these topological semimetals, as well as the effects of domain structures, their temporal dynamics and ultrafast switching, remain critical and still-wide-open questions. In this three-year project, the research team uses scanning and time-resolved magneto-optical Kerr effect microscopy and magneto-terahertz spectroscopy to study the domain evolution, the Berry curvature effect, and its dynamics in magnetic Weyl semimetals. The principal investigator aims to establish these techniques as a new platform to study magnetic topological materials that have been constantly emerging in the field. This project will help to establish the comprehensive fundamental understanding of various aspects of magnetic Weyl semimetals in both the real and momentum space and also their temporal dynamics in order to establish them as new platforms for topological spintronics and information processing. 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.