Theory of nonlinear cyclotron resonance in quasi-two-dimensional electron systems

Momentum and energy balance equations are developed for steady-state electron transport and optical absorption under the influence of a dc electric field, an intense ac electric field of terahertz (THz) frequency in a two-dimensional (2D) semiconductor in the presence of a strong magnetic field perpendicular to the 2D plane. These equations are applied to study the intensity-dependent cyclotron resonance (CR) in far-infrared transmission and THz-radiation-induced photoconductivity of GaAs heterostructures in Faraday geometry. We find that the CR peaks and line shapes of the transmittance exhibit different intensity dependence when the intensity of THz field increases in the range above or below a certain critical value. The CR in photoresistivity, however, always enhances with increasing the intensity of the THz field. These results qualitatively agree with the experimental observations. We have clarified that the CR in photoconductivity is not only the result of the electron heating, but also comes from photon-assisted scattering enhancement, especially at high temperatures. The effects of an intense THz field on Faraday angle and ellipticity of magnetically-biased 2D semiconductors have also been demonstrated.