CAREER: Observing topological magnetoelectric effects by magneto-optics and quantum transport

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NON-TECHNICAL DESCRIPTION: Quantum technologies can solve some of the world’s most challenging problems including medicine design, artificial intelligence and cyber security as well as fundamental physics and chemistry research. Therefore, their realization is crucial for national health, prosperity and security. In order to develop quantum technologies, new materials are needed in which quantum effects are pronounced and therefore can be accessed, controlled and harnessed. This project focuses on a particular quantum mechanical phenomenon called the magnetoelectric effect, which describes the coupling between electricity and quantum mechanical spin. By discovering and exploring novel materials, this project aims to achieve control of quantum spin by electrical means with unprecedented precision, efficiency and robustness. The project pushes the knowledge boundary of quantum physics, with the potential to make completely unexpected discoveries. The project trains next-generation quantum scientists and engineers. Graduates can find employment in academia in the area of fundamental quantum science research and in technology companies pursuing quantum technologies. This project also includes strong educational and outreach activities with particular focus on helping underrepresented groups by collaborating with a historically black research university and promoting STEM in K12 students and among the general public. TECHNICAL DESCRIPTION: This project aims to identify fundamentally new kinds of magnetoelectric effects that are uniquely enabled by the nontrivial topology and Berry curvature in topological materials. In sharp contrast to the magnetoelectric effects found in wide-gap magnetic insulators, the magnetoelectric effects in topological materials can exhibit unprecedented characters such as being quantized, diverging, and dissipationless. The project focuses on three classes of topological phases, Axion insulators, magnetic Weyl semimetals, and gyrotropic superconductors, and the project utilizes magneto-optics, nonlinear optics and quantum transport. The observation of topological magnetoelectric effect represents discoveries of new fundamental quantum physics, which pushes the frontiers of important topics of current quantum condensed matter research including topology, correlation, magnetism and spintronics. The topological magnetoelectric effects also open the door for urgently needed new device principles, most noticeably topological magnetoelectric devices, where simultaneous tuning of electrical and magnetic properties can be achieved without dissipation through a cohesive, multi-disciplinary approach involving electronics, physics and materials. The project contains unique education and outreach activities, including new teaching concepts to bridge and fuse physics and chemistry, collaboration with a historically black research university to create year-long research exchange activity, as well as promoting STEM in K-12 students and the general public by blending quantum science with cultural and art activities.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.