Raman-scattering spectra of elementary electronic excitations in coupled double-quantum-well structures

Using the time-dependent local-density approximation (TDLDA) within a self-consistent-linear response theory, we calculate the elementary excitation energies and the associated inelastic light-scattering spectra of a strongly coupled two-component plasma in a double-quantum-well system with electron occupation of symmetric and antisymmetric subbands. We find, consistent with the results of a recent experimental Raman-scattering study, that the intersubband spin-density excitations tend to merge with the single-particle excitations (i.e., the excitonic shift decreases monotonically) as the Fermi energy increases beyond the symmetric-antisymmetric energy gap ${\mathrm{\Delta }}_{\mathrm{SAS}}$. However, our TDLDA calculation does not show the abrupt suppression of the excitonic shift seen experimentally at a finite value of the subband occupancy parameter η==${\mathrm{\Delta }}_{\mathrm{SAS}}$/${\mathit{E}}_{\mathit{F}}$.