Quantum soliton hydrodynamics in magnetic insulators

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

NONTECHNICAL SUMARY This award supports theoretical research and education on developing a methodology for the description of spin transport in magnetic materials in analogy to hydrodynamics. Apart from carrying electric charge, electrons moving through materials carry with them a tiny magnetic moment called spin. Manipulation of those magnetic moments enables new kinds of electronic devices that utilize spin in addition to charge. There are circumstances under which the description of the transport of spins and of the magnetic arrangements (textures) that many spins collectively create can be achieved by analogy to the description of a fluid. The PI will develop a theoretical framework for describing how spin textures interact and flow through magnetic materials. The PI's research and collaboration with materials scientists and engineers at UCLA will help develop and support concepts for memory, logic, and communications devices that are based on materials that harness spin textures. In addition to research, the PI will continue and build upon his involvement with a successful outreach program run under the auspices of the UCLA California Nanosystems Institute, which brings nanoscience and nanotechnology experiments, along with theoretical explanations and presentations, to high-school students from public schools in the Los Angeles unified school district. The PI will also develop a condensed-matter-theory-centered component for UCLA's Research Experience for Undergraduates program, in which undergraduate students work with a faculty mentor, as well as other professors, researchers, and graduate students, on a summer research project. TECHNICAL SUMMARY This award supports theoretical research and education towards developing the theory of real-space topological hydrodynamics in relation to fluctuations and flows of topological solitons in magnetic insulators. The interplay of heat flows and spin dynamics in magnetic systems shifted much of the interest in the field of spintronics onto collective forms of spin transport. Important examples are topological spin textures, such as chiral domain walls and skyrmions, which have been realized and studied in a number of magnetic materials. Dynamic coupling effects between such textures and itinerant flows of quasiparticles has garnered attention in broad studies of nonequilibrium phenomena and transport in magnetism. Momentum-space topology, for quasiparticle bands in metals and insulators, has revitalized materials science research in classes of semiconductors, semimetals, superconductors, as well as magnetic insulators, with an eye on unusual forms of quantized response and gapless transport at the boundaries between distinct topological phases. Drawing on these developments, the PI will address the main problems along the following directions: long-range transport through ordered and frustrated quantum magnets, utilizing conservation laws based on spatially-delocalized topological invariants; exotic hydrodynamics and elasticity of emergent solitonic fluids and crystals; and developing a circuit-theory formalism for topological entanglement production with feasible spintronic and spin-caloritronic means. Spintronic structures and devices explored in this research will offer an alternative to superconducting quantum circuits as a versatile and scalable platform for quantum information processing and computing. In addition to research, the PI will continue and build upon his involvement with a successful outreach program run under the auspices of the UCLA California Nanosystems Institute, which brings nanoscience and nanotechnology experiments, along with theoretical explanations and presentations, to high-school students from public schools in the Los Angeles unified school district. The PI will also develop a condensed-matter-theory-centered component for UCLA's Research Experience for Undergraduates program, in which undergraduate students work with a faculty mentor, as well as other professors, researchers, and graduate students, on a summer research project.