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 approximation in a modulation-doped quantum well. The solution is then used 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 excitations in a δ-doped quantum well. Our theoretical method treats the exchange, depolarization, and excitonic effects on an equal footing and does 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 agreement between our theoretical results and those for the light-scattering experiments is shown.