Lifting of the Spin Degeneracy of Hole Subbands in a Surface Electric Field on Silicon

In hole space-charge layers on silicon we observe lifting of the quasispin degeneracy by the surface electric field in the absence of an external magnetic field. This lifting is detected in a splitting of intersubband resonance transitions and increases with increasing surface carrier density, reflecting an increase with quasimomentum. We have performed calculations of the subband excitation spectrum which confirm the experimentally observed quasispin splitting.