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arXiv · 2202.12151

Magnon corner states in twisted bilayer honeycomb magnets

Chun-Bo Hua·Feiping Xiao·Zheng-Rong Liu·Jin-Hua Sun·Jin-Hua Gao·Chui-Zhen Chen·Qingjun Tong·Bin Zhou·Dong-Hui Xu
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Abstract

Search for higher-order topological insulators, characterized by topologically protected gapless boundary states of codimension higher than one, in bosonic systems has attracted growing interest. Here, we establish twisted bilayer honeycomb magnets as a new platform for hosting second-order topological magnon insulators (SOTMIs) without fine-tuning. We employ a simple, minimal Heisenberg spin model to describe misaligned bilayer sheets of honeycomb ferromagnetic magnets with a large commensurate twist angle. We found that the higher-order topology in this bilayer system shows a significant dependence on the interlayer exchange coupling. The SOTMI, featuring topologically protected magnon corner states, appears for ferromagnetic interlayer couplings, while the twisted bilayer exhibits a nodal phase in the case of antiferromagnetic interlayer coupling.

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Chun-Bo Hua, Feiping Xiao, Zheng-Rong Liu, Jin-Hua Sun, Jin-Hua Gao, Chui-Zhen Chen, Qingjun Tong, Bin Zhou, Dong-Hui Xu. 2022-02-24. Magnon corner states in twisted bilayer honeycomb magnets. https://doi.org/10.1103/physrevb.107.l020404

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