  We present a theoretical study of magnetoplasmon spectrum of a
two-dimensional electron gas in the presence of Rashba spin-orbit interaction
(RSOI), one-dimensional weak electric modulation and a perpendicular magnetic
field. The intra-Landau-band magnetoplasmon spectrum is determined in the
presence of spin-orbit interaction within the self consistent field approach at
finite temperature. Due to Rashba effect, the spin of finite-momentum electrons
feels a magnetic field perpendicular to the electron momentum in the inversion
plane. The magnetoplasmon spectrum of the modulated two-dimensional electron
gas (M2DEG) system is found to exhibit beating of Weiss oscillations due to
Rashba effect which is the focus of this work. This effect is absent in the
magnetoplasmon spectrum of M2DEG if Rashba spin-orbit interaction is not taken
into account. In addition, our finite temperature theory ficilitates analysis
of effects of temperature on the magnetoplasmon spectrum of M2DEG in the
presence of RSOI. We find that the beating pattern is damped but continues to
persist at a finite but low temperature.
