“Half moons,” distinctive crescent patterns in the dynamical structure factor, have been identified in inelastic neutron scattering experiments for a wide range of frustrated magnets. In an earlier paper [H. Yan et al., Phys. Rev. B 98, 140402(R) (2018)] we have shown how these features are linked to the local constraints realized in classical spin liquids. Here, we explore their implication for the topology of magnon bands. The presence of half moons indicates a separation of magnetic degrees of freedom into irrotational and incompressible components. Where bands satisfying these constraints meet, it is at a singular point encoding Berry curvature of ±2⁢𝜋. Interactions which mix the bands open a gap, resolving the singularity, and leading to bands with finite Berry curvature, accompanied by characteristic changes to half-moon motifs. These results imply that inelastic neutron scattering can, in some cases, be used to make rigorous inference about the topological nature of magnon bands.

中文翻译：

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捏点和半月形编码 Berry 曲率


“半月”是动力学结构因子中独特的新月形图案，已在各种受挫磁体的非弹性中子散射实验中被确定。在之前的一篇论文 [H. Yan et al.， Phys. Rev. B98， 140402（R） （2018）] 中，我们展示了这些特征如何与经典自旋液体中实现的局部约束相关联。在这里，我们探讨了它们对磁振子带拓扑的意义。半月的存在表明磁性自由度分离为不旋转和不可压缩的分量。在满足这些约束的频带相遇的地方，它位于编码 ±2π 的 Berry 曲率的奇异点。混合条带的相互作用打开了一个缺口，解决了奇点，并导致具有有限 Berry 曲率的条带，并伴随着半月形图案的特征变化。这些结果表明，在某些情况下，非弹性中子散射可用于对磁振子带的拓扑性质进行严格推断。