Rashba effect within the space-charge layer of a semiconductor

The observed heavy-hole, light-hole and split-off band edges of a semiconductor are the well known consequence of two physical processes: atomic spin-orbital interaction and solid-state band-band anticrossing. In this work, we examined the four band-edge-like bands in great detail within the Ge space-charge layer with either Pb/Ge(111)-root 3 x root 3 R30 degrees or a 2ML Pb film on Ge(111). Our results reveal that the conventional picture of band edges for a semiconductor is actually crude. In addition, momentum-dependent Rashba splitting effect can be included to explain the observed non-split-off band, indicating the Rashba effect as an intrinsic property near a semiconductor surface.