AI 中文总结
本研究提出表面交替磁性（SAM）概念，建立对称性框架识别其存在的对称性破缺表面，经紧束缚与第一性原理计算验证，将交替磁性扩展至材料表面，为无外场自旋操控铺路。
AI 中文摘要
目前关于交替磁性的研究主要聚焦于磁性材料中的自旋极化体电子态。本研究通过引入表面交替磁性（Surface Altermagnetism, SAM）的概念推动该领域发展，其中交替自旋极化出现在共线反铁磁体（antiferromagnets, AFMs）或交替磁体（altermagnets, AMs）的表面。为构建该现象的理论基础，我们建立了基于对称性的完整框架，系统连接两类体系的体自旋群与表面自旋群。通过对称性分析，我们识别出所有可支撑SAM的对称性破缺表面，其中PT对称AFMs对应35种，体AMs对应61种不同情况。此外，我们证明203个共线自旋空间群（包括100个不含[C₂∥P]操作的空间群和103个含该操作的空间群）可通过分数平移对称性破缺，使tT对称AFMs表面出现SAM。该框架通过紧束缚模型和第一性原理计算得到验证，代表性化合物如NaMnP、LiMnAs和CrSb中均展示了实际材料实现。我们的结果确立SAM为一种鲁棒的、对称性保护的磁态，将交替磁性现象扩展至材料表面，为下一代自旋电子技术中无需外场的先进自旋操控铺平道路。
英文摘要
Research on altermagnetism has thus far primarily focused on spin-polarized bulk electronic states in magnetic materials. In this work, we advance the field by introducing the concept of surface altermagnetism (SAM), wherein altermagnetic spin polarization emerges at the surfaces of collinear antiferromagnets (AFMs) or altermagnets (AMs). To lay the theoretical groundwork for this phenomenon, we construct a thorough symmetry-based framework that systematically connects bulk spin groups to surface spin groups for both types of systems. Through symmetry analysis, we identify all symmetry-breaking surfaces capable of supporting SAM, identifying 35 for $PT$-symmetric AFMs and 61 distinct cases for bulk AMs. Moreover, we show that 203 collinear spin space groups---including 100 without and 103 with the $[C_2 \Vert P]$ operation---permit the appearance of SAM on the surface of $tT$-symmetric AFMs via the breaking of fractional translational symmetries. The proposed framework is verified using tight-binding models and first-principles calculations, with practical material implementations shown in representative compounds like NaMnP, LiMnAs, and CrSb. Our results establish SAM as a robust, symmetry-protected magnetic state, extending altermagnetic phenomena to material surfaces and paving the way for advanced, field-free spin manipulation in next-generation spintronic technologies.
Journal refPhys. Rev. Lett. (2026)
