Cyclotron resonance in two dimensions

At low temperature and in a narrow magnetic filed range an abrupt and unexpected splitting or broadening of the cyclotron absorption line of a two-dimensional electron gas at a GaAs/(GaAl) As interface is observed. This phenomenon is shown to be a universal characteristic of two-dimensional systems which is not keyed to Landau-level filling. The possibility that a softening of the two-dimensional magnetoplasmon mode may be responsible for this behavior is explored. © 1984 The American Physical Society.