Influence of nonparabolicity on collective intersubband spin- and charge-density excitation spectra

The influence of the conduction-band nonparabolicity on the collective spin and charge-density excitation spectra in GaAs/Alₓ{Ga}_{1{{-}}x}$As quantum wells is discussed theoretically in the framework of the local-density approximation. Emphasis is placed on estimating the importance of band population effects at finite temperature. A line-shape calculation shows that the nonparabolicity shifts resonance energies and leads to the additional broadening of the excitation spectra. Qualitatively different behavior of the linewidth (as a function of the electron concentration) is found for the charge- and spin-density excitations.