Optic and acoustic plasmon modes of a semiconductor superlattice

The collective plasmon modes of s semiconductor superlattices consisting of alternating layers of electrons and holes or alternating layers of electrons with different densities are investigated. For wells widely separated in space, such that Bloch wavefunction overlap between wells is negligible, we find optical-like and acoustical-like plasmon modes propagating along the superlattice direction. Perpendicular to the superlattice direction, the acoustic mode (ω～q_″) recently observed by Olego and Pinczuk⁸ is found to be split into two acoustic branches.