手性畴壁亚稳态的量子几何机制：在扭曲过渡金属二硫族化合物中的应用
A quantum geometric mechanism for chiral domain wall metastability: Application to twisted transition-metal dichalcogenides
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中文总结 AI 辅助
该研究提出手性畴壁亚稳态的量子几何机制，将其应用于扭曲过渡金属二硫族化合物，解释了相关实验现象，为探测能带量子几何提供了新方法。
中文摘要 AI 辅助
能带拓扑可对铁磁体的激发产生影响，一个已知例子是量子霍尔铁磁体及其晶格类似物；当两种味具有相同的陈数$C$时，光滑斯格明子纹理每单位缠绕会束缚电荷$-eC$。在此，我们转而考虑时间反演关联的共轭陈带情况。我们证明，尽管净电荷响应消失，光滑纹理仍可与偶极响应相关联——沿长度方向具有面内缠绕的畴壁（DW）可束缚垂直于畴壁的非零偶极密度。该偶极密度的强度由无量纲系数$c_G$控制。尽管几何偶极系数$c_G$未被量子化，但它是占据投影器在混合（动量和序参量）空间中第二陈形式的矩，通常非零。因此，偶极修饰的畴壁可因偶极排斥与常规表面张力的竞争，在有限塞曼场下于有限半径处变得亚稳态。在扭曲MoTe$_2$的实际模型中，我们发现$c_G$在谷极化（VP）相内从$C=1$铁磁体到$C=0$铁磁体的转变处急剧下降。这自然解释了最近在空穴填充$\nu=1$下的泵浦-探针实验[\text{exp}]，其中长寿命激发在远超饱和场的反向场中仍存在，但在中间位移场下消失，尽管常规磁诊断仅发生微弱变化。因此，亚稳态自旋纹理可作为能带量子几何的灵敏探针，且是陈共轭带中莫尔铁磁体快速光学控制的固有瓶颈。
英文摘要
Band topology can have an imprint on the excitations of a ferromagnet. A known example is quantum Hall ferromagnets and their lattice analogs; when both flavors have the same Chern number $C$, a smooth skyrmion texture binds charge $-eC$ per unit winding. Here, we consider instead the case of conjugate Chern bands related by time-reversal. We show that, despite the vanishing net charge response, a smooth texture can be associated with a dipole response---a domain wall (DW) with an in-plane winding along its length can bind a nonzero dipole density transverse to the wall. The strength of this dipole density is controlled by a dimensionless coefficient $c_G$. Although not quantized, the geometric dipole coefficient $c_G$ is a moment of the second Chern form of the occupied projector in mixed (momentum and order-parameter) space and is generally nonzero. The dipole-decorated DW can thus become metastable at a finite radius due to the competition between dipolar repulsion and the usual surface tension, even at a finite Zeeman field. In a realistic model of twisted MoTe$_2$, we find that $c_G$ drops sharply across a transition within the valley-polarized (VP) phase from a $C=1$ to a $C=0$ ferromagnet. This naturally explains recent pump-probe experiments~\cite{exp} at hole filling $ν=1$, in which a long-lived excitation survives reverse fields far exceeding the saturation field but disappears at an intermediate displacement field despite only weak changes in conventional magnetic diagnostics. Metastable spin textures thus serve as a sensitive probe of band quantum geometry, and as an intrinsic bottleneck for fast optical control of moiré ferromagnets in Chern-conjugate bands.
