Spontaneous Spin Polarization of Photoelectrons from GaAs

We observe a spontaneous electron-spin polarization in GaAs(110) in photoemission experiments using excitation with linearly polarized light. This effect is a consequence of the noncentrosymmetric crystal structure of GaAs and suggests that the polarization of each spin-split conduction band can be almost as high as ± 100%. A net nonzero polarization after summation over spin states arises from (a) differences in spin-up and -down conduction-band hybridization with valence $p$ states, and (b) surface-transmission effects.