Spin splitting in electronic band structures induced by antiferromagnetic order provides a new pathway to control spin-polarized carriers for spintronic applications. Here, we probe the spin degrees of freedom in the electronic band structure of the antiferromagnet NdBi using a laser-based spin- and angle-resolved photoemission spectroscopy (SARPES) system with micrometer-scale spatial resolution. Our measurements reveal that two surface bands in the antiferromagnetic state are spin-split and carry opposite spin polarizations. The spin polarization is antisymmetric with respect to the time-reversal-invariant momentum, showing that inversion symmetry breaking at the surface lifts spin degeneracy. Density-functional-theory calculations assuming a single-q antiferromagnetic structure reproduce the observed dispersions and spin textures, indicating that the spin-split surface states originate from the interplay between inversion-symmetry breaking and antiferromagnetic order. These findings establish NdBi as a platform to explore inversion-symmetry-controlled spin textures in antiferromagnets and highlight the power of laser-based micro-SARPES for probing spin-polarized electronic states.
Yamamoto et al. (Thu,) studied this question.