Optical hole in a two-dimensional electron gas

We consider optical transitions from occupied localized states in a quasi-two-dimensional electron gas to high-energy empty states in the conduction band. The cross section for these transitions is proportional to the density of states of a suddenly created hole in a localized level. We investigate the effect of low-frequency single-particle and collective excitations of the Fermi sea on the hole density of states. We find that gapless plasmons lead to the narrowing of the main singularity and to the structure at higher frequency associated with a hole-plasmon complex dressed by single-particle excitations.