Xianglin Ke, Michigan State University

"Probing Novel Magnetic Excitations in Low-Dimensional Magnets"

Abstract: Low-dimensional quantum magnetism has been one of actively pursued research topics in the past decades. In this seminar, I will present our recent neutron scattering and thermal transport studies of magnetic excitations in two low-dimensional magnets. The first one is a unique quasi-1D system, Cu2(OH)3Br, which consists of weakly-coupled, ferromagnetic and antiferromagnetic alternating chains. As a result, this system shows coexistence of two different magnetic quasiparticles: the ferromagnetic chains give rise to conventional magnon excitations, while the antiferromagnetic chains yield spinons. Furthermore, these two magnetic quasiparticles interact via weak interchain interactions, leading to gap opening of magnetic excitations and asymmetric spectral weight. The second example I will present is a 2D insulating van der Waals magnet VI3. This material exhibits an anomalous thermal Hall effect with large thermal Hall signal over a wide temperature region. The thermal Hall effect is of dual nature, dominated by topological magnons hosted by the ferromagnetic honeycomb lattice at higher temperatures while being driven by magnon polarons induced by magnon-phonon coupling at lower temperatures.