Abstract:
We analyze the spectra of electronic elementary
excitations in a double component plasma of photoinjected
electrons and holes in semiconductors under continuous
laser illumination. We show that in the resulting
nonequilibrium steady state four types of elementary
excitations of the photoinjected carrier system can be
identified. Two are the expected single quasi-particle
excitations and the higher frequency plasma wave. and two
novel ones at low frequencies labelled as acoustic plasma
waves that are we1 1 defined under particular conditions.
These acoustic branches are interpreted as corresponding to
the collective motion of each type of carriers interacting
through the screened part of Coulomb interaction.
