In half-metallic systems, electronic conduction is mediated by a single spin species, offering enormous potential for spintronic devices. Here, using microscopic-area angle-resolved photoemission, we show that a spin-polarised two-dimensional hole gas is naturally realised in the polar magnetic semiconductor AgCrSe₂ by an intrinsic self-doping at its CrSe₂-terminated surface. Through comparison with first-principles calculations, we unveil a striking role of spin-orbit coupling for the surface hole gas, unlocked by both bulk and surface inversion symmetry breaking, suggesting routes for stabilising complex magnetic textures in the surface layer of AgCrSe₂.

在半金属系统中，电子传导由单一自旋物种介导，为自旋电子器件提供了巨大的潜力。在这里，利用微观区域角分辨光电子发射，我们证明了自旋极化的二维空穴气是通过在极性磁性半导体AgCrSe _{2的CrSe 2}端接表面处的本征自掺杂自然实现的。通过与第一性原理计算的比较，我们揭示了表面空穴气体的自旋轨道耦合的显着作用，这是通过体相和表面反演对称性破缺解锁的，提出了稳定 AgCrSe 2 表面层复杂磁性织构的_途径。