Dispersion of two-dimensional plasmons in GaAs quantum well and Ag monolayer

• Corrections due to exchange-correlations and finite temperature are essential to explicate the measured 2D plasmon dispersion.
• Correlations are seen to introduce a noticeable red shift in plasmon frequency, while temperature has an opposite effect.
• At ultra low densities, the STLS theory seems to overestimate correlations which has the effect of over-suppressing plasmons into the single electron–hole pair continuum already at a relatively small q.
• The plasmon energy can be tuned to some extent by controlling the transverse confinement of 2D electrons.

We study theoretically the role of finite temperature, exchange-correlations and finite layer width in explicating experimental findings on dispersion of two-dimensional plasmons in GaAs single quantum well and Ag monolayer. The plasmon energy is obtained from the poles of electron density response function determined by using the finite-temperature self-consistent mean-field theory of Singwi et al. Except for ultra low electron densities (as in GaAs system), our results exhibit a reasonably good agreement with the experimental data. While correlations are found to introduce a noticeable red shift in plasmon frequency, temperature has an opposite effect. Both of these effects become increasingly important with reduction in electron density. At ultra low densities, our predictions agree only for small wave vectors (q<0.6kFq<0.6kF), with correlations over-suppressing plasmons into the single electron–hole pair continuum already at a relatively small q. This shortcoming may be arising due to the neglect of the dynamical nature of correlations in our study. Further, it is found that finite layer width gives rise to a red shift in plasmon dispersion, but its effect is significant when average electron-electron spacing is smaller than or comparable with layer width.

Our study underlines that the exchange-correlation and finite-T corrections are crucial to explicate the measured 2D plasmon dispersion. Figure given below compares our results (solid curve) for 33 nm wide GaAs QW with experiment (symbols) for density rs=8.7rs=8.7 and T=1.85 K. Other curves (from bottom) are zero-T, and the finite-T dynamical HA and RPA predictions.Figure optionsDownload as PowerPoint slide