MANY-BODY EFFECTS ON INTERSUBBAND SPIN-DENSITY AND CHARGE-DENSITY EXCITATIONS

A self-consistent solution is presented, which takes into account the k dependence of the subband wave functions under the Hartree-Fock appr oximation in a modulation-doped quantum well. The solution is then use d in a formulation, by solving numerically the Bethe-Salpeter equation for the corresponding polarization functions, to study the many-body effects on the intersubband spin-density and charge-density excitation s in a delta-doped quantum well. Our theoretical method treats the exc hange, depolarization, and excitonic effects on an equal footing and d oes not require any parametrization procedure, as has been used in the local-density approximation. We find that the excitonic binding tends to cancel the corrections due to exchange self-energies. Excellent ag reement between our theoretical results and those for the light-scatte ring experiments is shown.