Interacting intersubband excitations in parabolic semiconductor quantum wells.

Abstract

We calculate the finite wave-vector intersubband collective excitation spectra in wide parabolic wells at low two-dimensional electron densities where only the lowest quantum subband is occupied by electrons. We use a self-consistent time-dependent local-density approximation to calculate the linear response of the system, comparing our density-functional results with the noninteracting time-dependent Hartree approximation to estimate the magnitudes of exchange-correlation corrections to the collectivemode dispersion. We predict a qualitatively new phenomenon at low electron densities where, in the presence of exchange-correlation effects, it becomes possible for the collective charge-density excitation (i.e., the intersubband plasmon mode) to lie below the intersubband quasiparticle continuum