  We developed a theory describing elementary excitations in the Bose-Fermi
system induced by circularly polarized light in a two-dimensional (2D) gas of
charge carriers with different masses. In such a hybrid system, the Fermi
subsystem is a degenerate Fermi gas, whereas the Bose subsystem is a condensate
of the light-induced composite bosons consisting of two fermions (electrons or
holes) with different effective masses. The interaction of the single-particle
excitations and the collective excitations (plasmons) in the Fermi subsystem
with the Bogoliubov collective modes (bogolons) in the Bose subsystem is
analyzed. The renormalization and damping (lifetime) of the excitations are
calculated, and the possibility of their experimental observation is discussed.
The developed theory can be applied to describe 2D condensed-matter structures
containing charge carriers with different effective masses, including
transition metal dichalcogenide monolayers and semiconductor quantum wells.
