The effect of van der Waal's gap expansions on the surface electronic structure of layered topological insulators

On the basis of relativistic ab initio calculations, we show that an expansion of van der Waal's (vdW) spacings in layered topological insulators caused by intercalation of deposited atoms, leads to the simultaneous emergence of parabolic and M-shaped two-dimensional electron gas (2DEG) bands as well as Rashba-splitting of the former states. The expansion of vdW spacings and the emergence of the 2DEG states localized in the (sub) surface region are also accompanied by a relocation of the topological surface state to the lower quintuple layers, that can explain the absence of inter-band scattering found experimentally.