Discrete Plasmons in Finite Semiconductor Multilayers

We observe discrete plasmons in layered 2D electron gases with a large, but finite, number of periods. The two-fold degeneracy of plasmon modes with wavenumbers in the first Brillouin zone of the infinite system is lifted by the loss of planes of symmetry. These characteristic discrete plasmon doublets are measured in inelastic light scattering spectra of multilayer GaAs-(AlGa)As heterostructures.