Cyclotron resonance in two dimensions: Electron-electron interactions and band nonparabolicity

We present a theory for cyclotron resonance of a two-dimensional electron gas in a strong magnetic field, using a generalized single-mode approximation for the magnetoplasmons of the system. The effects of electron-electron interactions and band nonparabolicity are included. The consequences of nonparabolicity are qualitatively altered by electronic correlations. Mode crossings are found to occur for filling factors near 2.5. These crossings may be responsible for some unexplained cyclotron-resonance anomalies observed away from integral filling factors.