Collective charge-density excitations in two-component one-dimensional quantum plasmas: Phase-fluctuation-mode dispersion and spectral weight in semiconductor quantum-wire nanostructures

摘要

Collective charge-density excitation spectra of both a spatially separated two-component quasi-one-dimensional (1D) quantum plasma, as existing in a semiconductor double quantum-wire structure, and a 1D homogeneous electron-hole plasma, as appropriate for a photoexcited semiconductor quantum-wire system, are calculated within the two-component random-phase approximation. We find two phase-fluctuation collective modes, one (optical plasmon, OF) with energy proportional to q1n(qa)(1/2) is the total in-phase tout-of-phase) charge-density oscillation of the system and the other (acoustic plasmon, AP) with a linear energy dispersion as q-->0 is the neutral out-of-phase tin-phase) charge-density oscillation of the system for the situation where the two components have the same (opposite) charges, where q is the 1D wave vector and a is a characteristic 1D confinement size. In contrast to higher dimensional systems we find the neutral long wavelength AP mode to be generically undamped by Landau damping effects due to the severe suppression of single-particle excitations in 1D systems. We also investigate the effect of impurity scattering on the collective-mode dispersion and damping, and calculate the collective-mode spectral weight by obtaining the dynamical structure factor. We find that both OP and AP modes are overdamped by impurity scattering below some critical wave vector. We find that in the long wavelength limit the spectral weight is carried mostly by the OF, but the spectral weight of the undamped AP mode at finite (but not too large) wave vectors is comparable with that of the OP mode, making it viable to observe the AP mode in semiconductor quantum-wire systems. The effect of the interwire electron tunneling in a biwire system on the collective charge density excitation spectra is also studied. We discuss the mode dispersion and damping from an effective Luttinger liquid perspective as well and in some cases include local-field corrections in our calculations. [S0163-1829199)09115-8]. [References: 40]