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Condensed Matter > Strongly Correlated Electrons
Title: Topological Weyl magnons and thermal Hall effect in layered honeycomb ferromagnets
(Submitted on 23 Dec 2020 (v1), last revised 21 Sep 2021 (this version, v2))
Abstract: In this work, we study the topological properties and magnon Hall effect of a three-dimensional ferromagnet in the ABC stacking honeycomb lattice, motivated by the recent inelastic neutron scattering study of CrI$_3$. We show that the magnon band structure and Chern numbers of the magnon branches are significantly affected by the interlayer coupling $J_c$, which moreover has a qualitatively different effect in the ABC stacking compared to the AA stacking adopted by other authors. The nontrivial Chern number of the lowest magnon band is stabilized by the next-nearest-neighbour Dzyaloshinsky-Moriya interaction in each honeycomb layer, resulting in the hopping term similar to that in the electronic Haldane model for graphene. However, we also find several gapless Weyl points, separating the non-equivalent Chern insulating phases, tuned by the ratio of the interlayer coupling $J_c$ and the third-neighbour Heisenberg interaction $J_3$. We further show that the topological character of magnon bands results in non-zero thermal Hall conductivity, whose sign and magnitude depend on $J_c$ and the intra-layer couplings. Since the interlayer coupling strength $J_c$ can be easily tuned by applying pressure to the quasi-2D material such as CrI$_3$, this provides a potential route to tuning the magnon thermal Hall effect in an experiment.
Submission history
From: Shuyi Li [view email][v1] Wed, 23 Dec 2020 19:13:08 GMT (968kb,D)
[v2] Tue, 21 Sep 2021 22:19:25 GMT (1213kb,D)
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