AI 中文总结
本研究通过第一性原理计算揭示，CrSb薄膜的自旋分裂微观起源与块体不同，需长程晶胞间Cr-Sb等跳跃，且自旋分裂具强表面依赖性，为低维交替磁体自旋分裂调控提供了通用原理。
AI 中文摘要
交替磁体（Altermagnets）因具有动量依赖的自旋分裂，近期成为自旋电子学应用的有前景材料；其中金属CrSb因具有巨大的自旋分裂和高奈尔温度，尤其受关注。然而，块体CrSb与薄膜CrSb中不同自旋分裂行为的微观起源仍未得到解决。本研究采用第一性原理计算，系统探究了不同表面取向的CrSb薄片的电子结构。尽管所有被研究的薄片都保留了与交替磁体兼容的自旋群对称性，但它们呈现出明显不同的电子结构：(2$\bar{1}\bar{1}$0)薄片保留了显著的交替磁性自旋分裂，而(0001)和(10$\bar{1}$0)薄片则显示出几乎自旋简并的能带。研究表明，维度降低从根本上改变了交替磁性自旋分裂的微观起源：与块体CrSb不同，薄膜中的交替磁性自旋分裂需要长程的晶胞间共面Cr-Sb跳跃，而Sb-Sb跳跃提供额外贡献；这些跳跃路径的保留或抑制，解释了自旋分裂对表面的强依赖性。本研究的发现为理解低维体系中的交替磁性建立了微观机制，并为低维交替磁性材料中自旋分裂的调控提供了通用原理。
英文摘要
Altermagnets have recently emerged as promising materials for spintronic applications owing to their momentum-dependent spin splitting. Among them, metallic CrSb is particularly attractive owing to its giant spin splitting and high Néel temperature. However, the microscopic origin of the distinct spin-splitting behaviors in bulk and thin-film CrSb remains unresolved. Here, we systematically investigate the electronic structures of CrSb slabs with different surface orientations using first-principles calculations. Although all considered slabs preserve spin-group symmetries compatible with altermagnetism, they exhibit markedly different electronic structures: the (2$\bar{1}\bar{1}$0) slab retains pronounced altermagnetic spin splitting, whereas the (0001) and (10$\bar{1}$0) slabs display nearly spin-degenerate bands. We demonstrate that dimensional reduction fundamentally changes the microscopic origin of altermagnetic spin splitting. Unlike bulk CrSb, altermagnetic spin splitting in thin films requires long-range inter-unit-cell coplanar Cr--Sb hopping, while Sb--Sb hopping provides an additional contribution. The preservation or suppression of these hopping pathways explains the strong surface dependence of the spin splitting. Our findings establish a microscopic mechanism for understanding altermagnetism in reduced dimensions and provide a general principle for engineering spin splitting in low-dimensional altermagnetic materials.
