Topological bosonic excitations in frustrated magnetic systems

Topological band theory has emerged as one of the central themes in condensed matter physics. In analogy with electrons, the bosonic excitations from spin waves (magnons) and lattice vibrations (phonons) can also exhibit non-trivial topological properties in magnetic insulators with broken inversion or time reversal symmetry. In this talk, I will showcase two such examples: first, I shall discuss the topological magnons and the associated thermal Hall effect in a layered honeycomb ferromagnet [1] motivated by the discovery of CrI3. We find several topological phase transitions and Weyl magnon behavior induced by the interlayer coupling. Second, I will discuss another type of topological bosonic excitations, the polaritons, arising from the magnon-phonon hybridization in a monolayer antiferromagnet FePSe3 [2].

[1] Topological Weyl magnons and thermal Hall effect in layered honeycomb ferromagnets, S. Li and A. H. Nevidomskyy, Phys. Rev. B 104, 104419
[2] Topological magnon-phonon hybridization in two-dimensional antiferromagnets, J. Luo, S. Li, Z. Ye, R. Xu, H. Yan, J. Zhang, G. Ye, L. Chen, D. Hu, X. Teng, W. A. Smith, B.I. Yakobson, P. Dai, A. H. Nevidomskyy, R. He, H. Zhu (under review of Nature Communications)