L. Liu et al., STATIC AND DYNAMIC PROPERTIES OF COUPLED ELECTRON-ELECTRON AND ELECTRON-HOLE LAYERS, Physical review. B, Condensed matter, 53(12), 1996, pp. 7923-7931
We have investigated coupled layers of electron and hole liquids in se
miconductor heterostructures in zero magnetic field for densities r(x)
less than or similar to 20 using the Singwi-Tosi-Land-Sjolander self-
consistent formalism generalized for layers of unequal density. We cal
culate susceptibilities, local fields, pair correlation functions, and
the dispersion of the collective modes for a range of layer spacings.
We include cases where the densities in the two layers are not equal.
We find generally that static correlations acting between layers do n
ot have a large effect; on the correlations within the layers, For cou
pled electron-hole layers we find that as the spacing between the laye
rs decreases there is a divergence in the static susceptibility of the
liquid that signals an instability towards a charge-density-wave grou
nd state. When the layer spacing approaches the effective Bohr radius
the electron-hole correlation function starts to diverge at small inte
rparticle separations. This effect is a precursor to the onset of exci
tonic bound states but this is preempted by the charge-density-wave in
stability. The acoustic plasmon exhibits a crossover in behavior from
a coupled mode to a mode that is confined to a single layer. Correlati
ons sometimes push the acoustic plasmon dispersion curve completely in
to the single-particle excitation spectrum. For layers with different
densities the Landau damping within the single-particle excitation reg
ion is sometimes so weak that the acoustic plasmon can exist inside th
e region asa sharp resonance. We find for the electron-hole case that
proximity to the charge-density-wave instability has an unusual effect
on the dispersion of the optical plasmon mode.