Dispersion of collective intersubband excitations in semiconductor superlattices

Abstract
We report the observation, by inelastic light scattering, of the dispersion of collective intersubband excitations of electrons confined in GaAs quantum-well superlattices. The ability to probe plasmons with large in-plane wave vectors allows one the unique possibility to study excitations in the two-dimensional limit. Intrasubband plasmons in this regime are also observed for the first time. The results are interpreted with current theories which include estimates of many-body effects.