Observation of spin splitting in the surface electronic structure of antiferromagnet NdBi

TL;DR

This study demonstrates spin splitting in the surface electronic structure of antiferromagnetic NdBi, revealing spin-polarized surface bands caused by inversion symmetry breaking and antiferromagnetic order, with implications for spintronics.

Contribution

First observation of spin-polarized surface states in NdBi due to antiferromagnetic order and inversion symmetry breaking, supported by experimental and theoretical analysis.

Findings

Surface bands in NdBi are spin-polarized in opposite directions.

Spin polarization is antisymmetric to electron momentum.

Spin splitting is explained by inversion symmetry breaking and antiferromagnetic order.

Abstract

Spin splitting in electronic band structures via antiferromagnetic orders is a new route to control spin-polarized carriers that is available for spintronics applications. Here, we investigated the spin degree of freedom in the electronic band structures of the antiferromagnet NdBi using laser-based spin- and angle-resolved photoemission spectroscopy (laser-SARPES). Our laser-SARPES experiments revealed that the two surface bands that appear in the antiferromagnetic state are spin-polarized in opposite directions as a counterpart of the spin splitting. Moreover, we observed that the spin polarization is antisymmetric to the electron momentum, indicating that spin degeneracy is lifted due the breaking of inversion symmetry at the surface. These results are well reproduced by our density functional theory calculations with the single-q magnetic structure, implying that the spin-split surface state is determined by the breaking of inversion symmetry in concert with the antiferromagnetic order.