Fluctuation effects on the cyclotron resonance spectrum for a two-dimensional electron gas

Existing theories of the frequency-dependent magnetoconductivity of a two-dimensional electron gas are plagued by the appearance of divergences in the associated memory function. Here we show that such divergences may be removed by the inclusion of fluctuation effects in the calculation of the conductivity. Our calculations are based on a new approach (viz., by the use of a generalized quantum Langevin equation), to quantum transport, which we have recently expounded. Our results display splitting of the cyclotron absorption line, for a range of magnetic field values at low temperature, which was found experimentally by Schlesinger, Allen, Hwang, and Platzman. In addition, our theory gives a very good fit to the heretofore unexplained experimental results of Kennedy, Wagner, McCombe, and Tsui, concerning the increase of the cyclotron resonance mass with decreasing ns in certain regions. The fluctuation effects are most pronounced for small systems with low electron concentrations. © 1988 The American Physical Society