Surface states in a gapless semiconductor
D'yakonov M. I., Khaetskii A. V.
It is shown that gapless α-Sn and HgTe semiconductors have specific surface states, which are a superposition of the electron states in the valence band and in the conduction band. The effective mass, which determines the motion along the surface in these states, depends on the mass ratio of the free electron and the free hole.