  The dielectric function and plasmon modes of a two-dimensional electron gas
(2DEG) are studied in single- and double-quantum-well structures with Rashba
spin-orbit interaction (RSOI) in the framework of the random-phase
approximation. The RSOI splits each parabolic energy subband of a 2DEG into two
nonparabolic spin branches and affects the electronic many-body correlation and
dielectric properties of the 2DEG. The influence of the RSOI on the 2DEG
plasmon spectrum in single quantum wells appear mainly in three ways: 1) an
overall frequency lowering due to the energy band deformation; 2) a weak
frequency oscillation stemming from the spin-split energy band; and 3)an
enhancement of the Landau damping as a result of the emerging of the
inter-branch single-particle-excitation spectrum. In double quantum wells, the
above effects are enhanced for the optic plasmon mode but diminished for the
acoustic one.
