One-dimensional plasmon dispersion and dispersionless intersubband excitations in GaAs quantum wires

The energy and wave-vector dispersion of single-particle and collective excitations of the one-dimensional (1D) electron gas in GaAs quantum wires have been determined by resonant inelastic light scattering. In the 1D quantum limit the intrasubband plasmon displays the linear dispersion characteristic of 1D free-electron behavior. Quantitative agreement is found with calculations based on the random-phase approximation. In contrast, 1D intersubband excitations appear as dispersionless and have a negligible shift from the single-particle energy. This mode exhibits the unique Landau damping expected for a 1D system with two occupied subbands.