Multipoletronics Enabled by Collinear and Noncollinear Antiferromagnets

Colorado State University, Fort Collins CO

Investigators

Abstract

NONTECHNICAL SUMMARY Magnetic materials are central to technologies such as data storage, sensors, and emerging computing devices. Most of these technologies rely on the electrons' magnetic moment, which is like a tiny compass needle carried by electrons, to manipulate and store information. This project explores an exciting new frontier in magnetism, where instead of using simple compass-like moments, it focuses on more complex shapes of magnetism known as "multipole moments", which arise in materials where magnetic moment directions vary in intricate patterns across tiny atomic distances. These complex magnetic structures, especially those found in a class of materials called antiferromagnets, can generate new and useful material responses to electric currents or light, opening the door to entirely new types of electronic devices and sensors. The project will develop theoretical tools to understand how these magnetic shapes behave, how they can be controlled by electric currents or light, and how they can enable novel information processing methods that go beyond traditional electron-magnetism-based electronics (also known as spintronics). Educational efforts alongside the research include mentoring students at various levels, organizing a summer school on symmetry in magnetism, and creating accessible teaching materials that blend modern theory and hands-on computation. Together, these efforts aim to expand both the scientific knowledge and the workforce needed for developing next-generation quantum materials and devices. TECHNICAL SUMMARY This project develops the theoretical foundations and functional implications of multipoletronics, an emerging framework that describes magnetic materials using spin multipole moments as active degrees of freedom. It focuses on collinear as well as noncollinear antiferromagnets where conventional spin-based descriptions are insufficient. The research is organized into two complementary thrusts: Thrust I develops a multipole-based dynamical theory, bridging spin dynamical equations and approximate conservation laws giving rise to definitions of multipole currents. It also establishes a gauge-invariant formulation for computing spin multipole moments from first-principles calculations. Thrust II explores nonequilibrium phenomena, including current-driven switching between symmetry-distinct multipolar states and the role of wave-packet multipole moments in interfacial transport. The combined effort provides new insights into complex spin textures, spin-orbit couplings, and topological band degeneracies in antiferromagnets and related quantum materials. Educational efforts alongside the research include mentoring students at various levels, organizing a summer school on symmetry in magnetism, and creating accessible teaching materials that blend modern theory and hands-on computation. Together, these efforts aim to expand both the scientific knowledge and the workforce needed for developing next-generation quantum materials and devices. 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.