CAREER: Band-Topology of Multipolar Magnetic Excitations

University Of California-Irvine, Irvine CA

Investigators

Abstract

This award is funded in part under the American Rescue Plan Act of 2021 (Public Law 117-2). NONTECHNICAL SUMMARY This award supports theoretical research aimed at the discovery and understanding of exotic properties of magnetic quantum materials. Instead of examining the individual attributes of electrons, considering their collective behavior reveals many remarkable properties of matter, including the generation of magnetism. The interplay of the electrons' spin and orbital degrees of freedom can produce novel states that behave very differently from the original constituents and bear great relevance for technological applications. This project focuses on understanding the conditions for such emergent states of matter and aims to uncover new features that facilitate their experimental detection and control. Specifically, this research integrates theoretical tools rooted in the modern concepts of topology and symmetries to characterize novel magnetic states. Furthermore, it establishes a connection between the theoretical description and the materials' responses to different experimental probes. Considering real materials in collaboration with experimental groups is an integral part of the research design. The results of this study can open new routes to low-energy consuming reconfigurable devices that build on magnetism and optical control. This award also supports outreach efforts to decrease the STEM opportunity gap of students from underserved and marginalized communities. This will be addressed on multiple levels of education, from elementary to graduate school, aiming to spark interest in sciences, build scientist identity, reduce the preparation gap, and improve the retention of underrepresented minorities. In particular, the PI will initiate summer programs, a physics Bootcamp, and a biennial graduate summer school and join an existing outreach activity at her institution targeting middle school students to promote awareness of existing opportunities and to help them visualize a future in higher education. TECHNICAL SUMMARY This award supports theoretical research aimed at the discovery and understanding of the exotic properties of quantum magnets. Magnetic materials endowed with a multi-component local Hilbert space have an extraordinary potential for realizing novel topological states. They admit unconventional multipole degrees of freedom, calling for a generalized approach to characterize their topology and experimental signatures. In particular, this research will explore how the enlarged local Hilbert spaces originating from the combination of spin, orbital, and lattice degrees of freedom can provide an internal structure to protect the nontrivial topologies. Furthermore, it will reveal how they can realize novel experimental probes for topological boundary modes based on the magneto-electric effect, surface-selective optical responses, and distinctive Hall signals. The results of this study will advance our understanding of the band-topology of multipole magnetic excitations and uncover unique experimental fingerprints for their detection and manipulation. Moreover, they will be directly relevant for a wide range of bosonic systems, including but not limited to photonic, acoustic, and mechanical lattices and artificial magnonic metamaterials. This award also supports outreach efforts to decrease the STEM opportunity gap of students from underserved and marginalized communities. This will be addressed on multiple levels of education, from elementary to graduate school, aiming to spark interest in sciences, build scientist identity, reduce the preparation gap, and improve the retention of underrepresented minorities. In particular, the PI will initiate summer programs, a physics Bootcamp, and a biennial graduate summer school and join an existing outreach activity at her institution targeting middle school students to promote awareness of existing opportunities and to help them visualize a future in higher education. 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.