We present a theory of the magnetoplasmon excitation spectrum in a two-dimensional electron gas for integral filling factors, by calculating the dynamical structure factor within the framework of the time-dependent Hartree-Fock approximation. We include collisional-broadening effect in the dynamical polarizability function in a relaxation-time approximation. We find that to account for the experimentally observed light-scattering spectra, we must introduce a phenomenological breakdown of wave-vector conservation in the dynamical structure factor. For reasonable phenomenological models of the violation of wave-vector conservation (which, for example, may arise from impurities and disorder), we find good agreement with the experimental data. Our calculation resolves the origin of the asymmetric magnetoplasmon band in the Raman intensity spectra for filling factor ν=1, whereas for ν=2, it identifies the peak of the scattering intensity between the roton minimum and the maximum of the dispersion relation in low-mobility samples.

• Received 18 February 1992

DOI:https://doi.org/10.1103/PhysRevB.45.13396