Excitations of the strongly correlated electron liquid in coupled layers

Abstract

The low lying excited states in a system of coupled layers of electrons in a gallium arsenide heterostructure are strongly affected by many-body correlations between the electrons for densities as high as ${\mathit{r}}_{\mathit{s}}$=5. For a layer spacing of less than 100 nm the function Im\ensuremath{\chi}(q,\ensuremath{\omega}) near q=1.9${\mathit{k}}_{\mathit{F}}$ has a large peak at small \ensuremath{\omega} which is apparently a soft-mode precursor to a charge density wave instability. This new peak should be observable with present experimental techniques in realistic samples. The linear gradient of the ``acoustic'' plasmon is depressed so much by many-body effects that for ${\mathit{r}}_{\mathit{s}}$=5 it can become degenerate with the single-particle excitation spectrum for all q.