YMn6⁢Sn6 consists of two types of Mn-based kagome planes stacked along the 𝑐-axis having a complex magnetic interaction. We report a spin reconstruction in YMn6⁢Sn6 from ferromagnetic (FM) into a combination of two incommensurate spin spirals (SSs) originating from two different types of Mn kagome planes driven by frustrated magnetic exchanges along the 𝑐-axis with the inclusion of the Hubbard 𝑈. The pitch angle and wave vector of the incommensurate SSs are ∼89.3∘ and ∼ (0 0 0.248), respectively, which are in excellent agreement with the experiment. We employ an effective model Hamiltonian constructed out of exchange interactions to capture the experimentally observed nonequivalent nature of the two incommensurate SSs which also explain the FM-SS crossover due to antiferromagntic spin exchange with correlation. We further report the existence of a topological magnon with spin-orbit coupling in the incommensurate SS phase of YMn6⁢Sn6 by calculating the topological invariants and Berry curvature profile. The location of the Dirac magnon in the energy landscape at 73 meV matches with another experimental report. We demonstrate the accuracy of our results by highlighting the experimental features in YMn6⁢Sn6.

中文翻译：

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拓扑磁振子在交换挫折驱动不相称的 kagome-latticeYMn6Sn6 自旋螺旋


YMn6Sn6 由两种类型的基于 Mn 的笼目平面组成，它们沿 c 轴堆叠，具有复杂的磁相互作用。我们报道了 YMn6Sn6 中的自旋重建，从铁磁 （FM） 到两个不相称的自旋螺旋 （SS） 的组合，这些自旋螺旋起源于两种不同类型的 Mn kagome 平面，由沿 c 轴的受挫磁交换驱动，包括哈伯德 U。不相称的 SS 的俯仰角和波矢分别为 ∼89.3∘ 和 ∼ （0 0 0.248），与实验结果吻合极好。我们采用由交换相互作用构建的有效模型哈密顿量来捕获实验观察到的两个不相称的 SS 的非等效性质，这也解释了由于反铁正旋交换与相关性而导致的 FM-SS 交叉。通过计算拓扑不变量和 Berry 曲率剖面，我们进一步报道了在 YMn6Sn6 不相称的 SS 相中存在具有自旋轨道耦合的拓扑磁振子。狄拉克磁振子在能源景观中的位置为 73 meV，这与另一份实验报告相匹配。我们通过强调 YMn6Sn6 中的实验特征来证明我们结果的准确性。