AI 中文总结
本研究利用共振超快泵浦-探测光谱，在扭转MoTe2莫尔超晶格的QAH磁体中观测到亚稳态手性畴壁，揭示了拓扑磁体自旋激发的量子几何效应，为理解拓扑保护稳定性提供关键见解。
AI 中文摘要
拓扑与关联的相互作用可产生奇异的集体激发。二维（2D）平带系统中近期发现的整数和分数量子反常霍尔（QAH）磁体，被预测会承载与常规磁体不同的自旋激发。然而在实验上，这些新型激发仍在很大程度上未被探索。本文中，我们利用共振超快泵浦-探测光谱，研究了扭转MoTe2莫尔超晶格中的自旋-谷激发。我们在温度T ~ 3.7 K以下的QAH磁体中观测到一种亚稳态自旋-谷激发，该激发可在比饱和磁场大几倍的反向磁场下存续。这种激发的行为与普通畴壁和磁振子截然不同，表明其是拓扑磁体特有的新型自旋-谷织构。我们提出，这些织构是手性畴壁，具有赝自旋序参量沿畴壁的面内缠绕。其亚稳态源于实空间的拓扑缠绕与动量空间中母带的量子几何之间通过一种普适机制产生的相互作用。这些手性畴壁主导着QAH磁体的非平衡动力学，且可能在其稳定性中发挥核心作用。本研究凸显了拓扑磁体中自旋激发的内禀量子几何效应，为理解限制拓扑保护稳定性的基本机制提供了关键见解。
英文摘要
The interplay between topology and correlation can give rise to exotic collective excitations. The integer and fractional quantum anomalous Hall (QAH) magnets recently discovered in two-dimensional (2D) flatband systems are predicted to host spin excitations distinct from those in conventional magnets. Experimentally, nevertheless, these new excitations remain largely unexplored. Here we investigate spin-valley excitations in a twisted MoTe2 moiré superlattice using resonant ultrafast pump-probe spectroscopy. We observe a metastable spin-valley excitation in the QAH magnet below T ~ 3.7 K that survives reverse magnetic field several times larger than the saturation field. The behavior of this excitation is sharply distinct from ordinary domain walls and magnons, indicating a new type of spin-valley textures unique to topological magnets. We propose that these textures are chiral domain walls with an in-plane winding of the pseudospin order parameter along the domain wall. Their metastability arises from the interplay between the topological winding in real space and the quantum geometry of the parent bands in momentum space through a universal mechanism. These chiral domain walls govern the nonequilibrium dynamics of QAH magnets and may play a central role in their stability. Our study highlights intrinsic quantum geometry effects on spin excitations in topological magnets; and provides key insights into the fundamental mechanism limiting stability of topological protection.
Comments4+10 figures
