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

•The Cs adsorbed H-Gabi surface forms a dipole moment capable of reducing the work function, thereby producing negative electron affinity (NEA) characteristics.•s and p orbitals appear the band inversion by spin-orbit couling, showing H-Gabi surface owns topologically non-trivial surface states.•Spin down electrons in x direction are efficient and selective spintronic emission, which have wide application in 2D spintronic device.