Negative electron affinity driven topological spin-polarized electrons in cesium adsorbed H-GaBi surface

III-V photocathodes with highly sensitive photoelectric response and broad spectral response exhibit great potential as key components for optoelectronic devices. However, these traditional III-V materials only possess the charge response without spin electrons, limiting the applications of spin-polarized detection. Herein, we report a type of III-V material, Cs adsorbed H-GaBi surface, in which the emissions of topological spin electrons are enhanced by negative electron affinity (NEA). We find that the dipole moment is formed on the surface of H-GaBi when adsorbing Cs atom, which is beneficial to reduce the work function (as low as 1.18 eV), resulting in the appearance of NEA (χ = −0.18 eV). At the meantime, such Cs@H-GaBi surface owns topologically non-trivial edge states: with the introduction of spin–orbit coupling (SOC), the band inversion of the s and p orbitals is appeared, and the spin down electrons in x direction are most likely to transfer. Therefore, under the NEA effect, vacuum energy level is located in the forbidden band region of trivial states, and topological spin electrons spontaneously enter the vacuum when passing through the vacuum energy level, resulting in efficient and selective spintronic emission.