ANOMALOUS LINESHAPE OF A CYCLOTRON-RESONANCE IN 2D ELECTRONIC SYSTEMS

The lineshape of a cyclotron resonance in a two-dimensional electron g as is analyzed. It is shown that depending on the value of magnetic fi eld B, two qualitatively different types of resonant absorption can ar ise. If the resonance value of magnetic field falls within the region where the dc Hall conductivity is quantized at low temperatures, than the resonance, absorption lines are damped and broadened at temperatur es T < W (W being the width of the mobility pp). With increase of the temperature (W less-than-or-equal-to T much less than nu(eff), nu(eff) is the frequency of electron-phonon relaxation) the amplitude of the resonance, line grows, attains its maximum and then decreases at T gre ater-than-or-equal-to nu(eff). In the case when the resonance absorpti on is observed in the region off the Quantum Hall Effect steps, the te mperature dependence of the resonance amplitude is normal.