Theory of combined exciton-cyclotron resonance in a two-dimensional electron gas: The strong magnetic-field regime

I developed a theory of combined exciton-cyclotron resonance ~ExCR! in a low-density two-dimensional electron gas in high magnetic fields. In the presence of excess electrons an incident photon creates an exciton and simultaneously excites one electron to higher-lying Landau levels. I derived exact ExCR selection rules that followed from the existing dynamical symmetries, magnetic translations and rotations about the magnetic field axis. The nature of the final states in ExCR is elucidated. The relation between ExCR and shake-up processes is discussed. The double-peak ExCR structure for transitions to the first electron Landau level is predicted.