Magnetic materials offer a fertile playground for fundamental physics discovery, with not only electronic but also magnonic topological states intensively explored. However, one natural material with both electronic and magnonic nontrivial topologies is still unknown. Here, we demonstrate the coexistence of first-order topological magnon insulators (TMIs) and electronic second-order topological insulators (SOTIs) in 2D honeycomb ferromagnets, giving rise to the nontrivial corner states being connected by the charge-free magnonic edge states. We show that, with C3${\mathcal{C}}_3$ symmetry, the phase factor ± ϕ caused by the next nearest-neighbor Dzyaloshinskii–Moriya interaction breaks the pseudo-spin time-reversal symmetry T$\mathcal{T}$, which leads to the split of magnon bands, i.e., the emergence of TMIs with a nonzero Chern number of C=−1$\mathcal{C}=-1$, in experimentally feasible candidates of MoI₃, CrSiTe₃, and CrGeTe₃ monolayers. Moreover, protected by the C3${\mathcal{C}}_3$ symmetry, the electronic SOTIs characterized by nontrivial corner states are obtained, bridging the topological aspect of fermions and bosons with a high possibility of innovative applications in spintronics devices.

中文翻译：

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二维铁磁体中电子和磁子拓扑态的耦合


磁性材料为基础物理发现提供了肥沃的游乐场，不仅对电子拓扑态而且对磁波拓扑态也进行了深入探索。然而，一种同时具有电子和磁波非平凡拓扑的天然材料仍然未知。在这里，我们证明了二维蜂窝铁磁体中一阶拓扑磁振子绝缘体（TMIs）和电子二阶拓扑绝缘体（SOTI）的共存，从而产生由无电荷磁振子边缘态连接的非平凡角态。我们发现，在 C3 对称性下，由下一个最近邻 Dzyaloshinskii-Moriya 相互作用引起的相位因子 ± phi 打破了赝自旋时间反转对称性 T，从而导致磁振子带的分裂，即 TMI 的出现在实验上可行的 MoI ₃ 、 CrSiTe ₃ 和 CrGeTe ₃ 单层候选材料中，C=−1 的非零陈数。此外，在 C3 对称性的保护下，获得了以非平凡角态为特征的电子 SOTI，将费米子和玻色子的拓扑方面联系起来，在自旋电子器件中具有很高的创新应用可能性。