AI 中文总结
该研究结合第一性原理计算与紧束缚模型，在AV₂X₂O反常磁体中分离出自旋-谷锁定节线费米子，确立其为探索拓扑自旋-谷锁定的通用平台。
AI 中文摘要
晶体对称性可稳定具有独特电子性质的拓扑态，而反常磁体（altermagnets）表现出无净磁化的动量依赖自旋劈裂。本文结合第一性原理计算与最小紧束缚模型，在d波反常磁体AV₂X₂O（A为Rb、Cs或K；X为Te、Se或S）中实现C配对的自旋-谷锁定节线费米子。低能电子结构在费米能级附近的C₄z配对谷周围共存自旋简并与自旋极化节线，自旋极化节线受面外镜面对称性M_z保护，且对自旋轨道耦合具有鲁棒性。最小模型揭示其微观起源并确立分离它们的通用设计原则，层工程与电子关联是在费米能级附近实现这些孤立自旋-谷锁定节线的材料调控旋钮，研究结果确立AV₂X₂O家族为探索d波反常磁体中拓扑自旋-谷锁定的通用平台。
英文摘要
Crystalline symmetries stabilize topological states with distinct electronic properties, while altermagnets exhibit momentum-dependent spin splitting without net magnetization. Here, we combine first-principles calculations with a minimal tight-binding model to realize $C$-paired spin-valley-locked nodal-line fermions in the $d$-wave altermagnet $\mathrm{AV_2X_2O}$ (A = Rb, Cs, or K; X = Te, Se, or S). The low-energy electronic structure hosts coexisting spin-degenerate and spin-polarized nodal lines around $C_{4z}$-paired valleys near the Fermi level. The spin-polarized nodal lines are protected by the out-of-plane mirror symmetry $\mathcal{M}_z$ and remain robust against spin-orbit coupling. The minimal model reveals their microscopic origin and establishes a general design principle for their isolation. Layer engineering and electronic correlations serve as material-specific knobs for realizing these isolated spin-valley-locked nodal lines near the Fermi level. Our results establish the $\mathrm{AV_2X_2O}$ family as a versatile platform for exploring topological spin-valley locking in $d$-wave altermagnets.
