Collective excitations of a two-component one-dimensional quantum plasma confined in semiconductor quantum wires

The collective plasmon excitation spectrum of a one-dimensional electron gas confined in a GaAs quantum wire is calculated within the two-subband random-phase approximation. We calculate the collective-charge-density-excitation (CDE) dispersion assuming that both the ground and the first excited subband states are occupied by electrons. We find four different branches of CDE modes, two of which are intrasubband CDE's and the other two intersubband CDE's. The mode-coupling effect between them is investigated by introducing a parity-breaking asymmetry in the confinement potential. Our calculated mode dispersion is in excellent quantitative agreement with a recent inelastic-light-scattering experiment.