  The screening of an individual low-dimensional object can be strongly
influenced by the objects nearby. We propose that such environment's influence
can be absorbed into an effective polarizability, instead of its intrinsic
polarizability. Using a toy system consists of two spatially separated 2DEG
layers gas an example, this picture is analytically deduced via a
multi-component RPA theoretical method. We show that the resultant effective
polarizability of backside layer is just the dielectric function describing the
system's collective plasmon excitations. Furthermore, several interesting
topics are discussed, e.g. the mutual modulation of Friedel oscillation, the
ultimate screening limit imposed by metal layer, smoothing potential
inhomogeneity in back screening configuration.
