Raman scattering by coupled intersubband-Landau-level excitations in quantum-well structures

We report on a Raman-scattering investigation of coupled intersubband-Landau-level excitations in GaAs quantum-well structures. Coupling was induced by tilting the magnetic field away from the superlattice axis. The samples were nominally undoped. Carriers at low concentrations (10⁹ cm^-2) were generated by means of photoexcitation. Data on various transitions at small tilt angles show very good agreement with results of perturbation theory and, at large angles, with calculations using a finite-basis approximation. Gaps in the excitation spectrum and signatures of the related persisting mixing of levels have been clearly observed. The lowest-lying coupled modes exhibit scaling behavior, following extremely well predictions of the parabolic-well model.