Visualizing the bulk-boundary correspondence in antiferromagnetic topological matter

Nontechnical Abstract Future quantum technologies depend heavily on novel quantum materials and their exotic electronic properties. This research project focuses on exploring the electronic characteristics of a unique class of materials known as magnetic topological insulators. Unlike conventional materials, topological materials exhibit distinct electronic states at their edges, surfaces, or even corners. These states are exceptionally robust, protected by the material's topology, making them resistant to disruptions from defects and impurities. To investigate these materials experimentally, the research team utilizes a scanning tunneling microscope, an instrument that enables visualization of atoms and electrons on a material's surface with atomic precision. With this tool, the team is examining the surfaces, edges and corners of topological materials and probing the electronic states present at these boundaries. These studies are expected to significantly enhance our understanding of novel topological phenomena, potentially driving advances in computing and materials science. The research project also includes outreach activities for K-12 students, featuring tabletop demonstrations and hands-on experiments with cryogenic cooling and superconducting levitation. Additionally, the principal investigator plans to write a scientific article for non-specialists on magnetic topological materials, highlighting insights gained from scanning tunneling microscopy. Technical Abstract Quantum materials exhibiting magnetism and higher-order topology represent a fascinating frontier in condensed matter physics. These materials feature robust and exotic electronic modes at their surfaces, hinges (edges), and even corners, protected by the topological properties and symmetries of their bulk. This research project investigates quantum materials with a strong interplay between antiferromagnetism, electronic correlations, and non-trivial topology. Specifically, the focus is on studying the axion insulator state and the emergent hinge and corner modes in three-dimensional antiferromagnetic topological matter. To achieve this, the research team employs spectroscopic imaging with the scanning tunneling microscope, an ideal tool for directly visualizing localized boundary modes at or near atomic steps, as well as their energy-momentum structure and non-trivial topology. This research also has broader impacts through outreach activities designed to captivate and inspire K-12 students. These activities include live demonstrations and hands-on experiments, such as cryogenic cooling and superconducting levitation, conducted during major soccer tournaments. Additionally, the principal investigator plans to write a scientific article for non-specialists about magnetic topological materials from the perspective of scanning tunneling microscopy. 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.