Inelastic Light Scattering by the High Mobility Two-Dimensional Electron Gas

We present a review of inelastic light scattering studies of two-dimensional electron systems in GaAs-AlGaAs heterostructures of ultrahigh electron mobility. In the case of intersubband excitations, between different confined states, the spectra show single-particle excitations in addition to collective spin-density and charge-density excitations. These results reveal exchange Coulomb interactions larger than previously anticipated. Light scattering spectra by large wave vector inter-Landau-level excitations of the 2D election gas in a high perpendicular magnetic field display the excitonic binding and magnetoroton minima in the mode dispersion that are predicted by Hartree-Fock theories.