Interlevel electromagnetic response of systems of spherical quantum dots

Interlevel electromagnetic response of individual spherical quantum dots (SQDs) as well as of two-dimensional (2D) rectangular lattice of spherical quantum dots is considered employing the self-consistent field approach in the quasistatic limit. It is established that the response can be considerably affected by the dynamic direct intradot and interdot electron-electron interaction. It is shown that the effects of these intradot and interdot interactions on the response can be analyzed separately. We show that correct description of the Coulomb coupling must take into account relevant umklapp processes. Fundamental importance of the problem of the electron self-interaction in quantum dot systems is established. The values are found which can be used for instant approximate estimation of the resonant dynamic screening (the depolarization shift) in any single SQD and 2D square lattice of SQDs. The effect of the size parameters of the systems, the SQD radius R and the lattice period d (and, in part, the three-dimensionality of the systems) on the depolarization shift is thoroughly investigated. Effect of polarization of incident radiation is investigated too. It is shown that the difference between the resonant photon energies for the normal and in-plane light polarization can be treated as independent of the static interdot interaction. Two-state and four-state electron systems are considered. Numerical calculations of the absorption spectra are performed for short period (d/2R <= 5) lattices of GaAs spherical quantum dots in the Al0.3Ga0.7As medium. It is established that the approximation of the point dipole-dipole interaction can be used for adequate representation of the dynamic interdot electron-electron interaction in the lattice. Also it is shown that the approach of the modified oscillator strength reproduces the absorption spectra of the considered systems with interacting modes of the collective excitation very well.