We have calculated the self-polarization energies for partially confined excitons by using the effective mass approximation and in the strong confinement regime. In order to avoid the unphysical divergence introduced by the step-like model for the dielectric function er, we have defined a finite size dielectric interface in which the er changes smoothly from its dot value up to the matrix value. The validity of the macroscopic dielectric approach was checked performing complementary calculations considering a coordinate-and size-dependent dielectric function. We have found that, depending on the thickness of the interface, the self-polarization energy S can reach very different values having a direct impact on the excitonic energies, which can be greater than those corresponding to a perfect confinement or practically zero for a wide range of dot sizes.
The interplay of tunneling, Coulomb coupling, and many-body effects on the charge-density (CDE) and spin-density (SDE) excitations of double quantum well systems has been analyzed. For increasing inter-well distances, the system moves from the strong-tunneling regime (one-well limit) towards the zero-tunneling but still strongly Coulomb coupled regime. Important renormalizations due to many-body effects are found in the long-wavelength limit of the CDE and SDE, with the latter exhibing a soft-mode in the intermediate tunneling, low-density regime.
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