Topological Magnon Insulator in Insulating Ferromagnet
Topological Magnon Insulator in Insulating Ferromagnet
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DOI：
10.1103/physrevb.87.144101
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发表时间：
2012-10
影响因子：
3.7
通讯作者：
Lifa Zhang;Jie Ren;Jian-Sheng Wang;Baowen Li
中科院分区：
文献类型：
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作者：
Lifa Zhang;Jie Ren;Jian-Sheng Wang;Baowen Li
在具有 Dzyaloshinskii-Moriya 相互作用的铁磁绝缘体中，我们从理论上预测并数值验证了拓扑磁振子绝缘体，其中无电荷磁振子受到拓扑保护，可以沿边缘/表面传输，同时其整体绝缘。手性边缘态在自旋波向量空间中形成一个连通环，作为 $4\ensuremath{\pi}$- 或 $8\ensuremath{\pi}$-period M\"obius 带，显示了磁能带的非平凡拓扑。使用非平衡格林函数方法，我们明确证明了单向手性边缘传输确实在拓扑上受到了缺陷或紊乱的保护。此外，我们表明拓扑边缘态主要集中在边缘周围，并且尽管手性边缘磁振子和能量流更喜欢沿着一个边缘从热区传播到冷区，但在另一边缘发现了异常传输，这些异常传输从冷区反向流向热区，我们的发现可以在各种磁振子晶体（例如 Lu${}_{2}$V${}_{2}$O${}_{7}$）中得到验证。
In the ferromagnetic insulator with the Dzyaloshinskii-Moriya interaction, we theoretically predict and numerically verify a topological magnon insulator, where the charge-free magnon is topologically protected for transporting along the edge/surface while it is insulating in the bulk. The chiral edge states form a connected loop as a $4\ensuremath{\pi}$- or $8\ensuremath{\pi}$-period M\"obius strip in the spin-wave vector space, showing the nontrivial topology of magnonic bands. Using the nonequilibrium Green's function method, we explicitly demonstrate that the one-way chiral edge transport is indeed topologically protected from defects or disorders. Moreover, we show that the topological edge state mainly localizes around edges and leaks into the bulk with oscillatory decay. Although the chiral edge magnons and energy current prefer to travel along one edge from the hot region to the cold one, the anomalous transports are identified in the opposite edge, which reversely flow from the cold region to the hot one. Our findings could be validated within wide energy ranges in various magnonic crystals, such as Lu${}_{2}$V${}_{2}$O${}_{7}$.