  Cyclotron resonance (CR) is considered one of the fundamental phenomena in
conducting systems. In this paper, we study CR in a gated two-dimensional (2D)
electron system (ES). Namely, we analyze the absorption of electromagnetic
radiation incident normal to the gated 2DES, where a standard dielectric
substrate separates the 2D electron sheet and the metallic steering electrode
("gate"); the whole system is placed in the perpendicular magnetic field. Our
analysis reveals the redshift of the absorption peak frequency compared to the
electron cyclotron frequency. The redshift appears in low-frequency regime,
when the resonant frequency is much less than the frequency of Fabry-Perot
modes in natural resonator "2D electron sheet - substrate - gate". Moreover, we
find this shift to be dependent on the electron density of 2DES. Therefore, it
can be controlled by varying the gate voltage. We predict that the shift can be
large in realistic gated or back-gated 2DESs. The obtained controllability of
CR in gated 2DES opens the door for exploring new physics and applications of
this phenomenon.
