Spin-resolved cyclotron resonance in InAs quantum wells: A study of the energy-dependent g factor

We report the observation of the spin-doublet splitting of cyclotron resonance (CR) in a two-dimensional electron gas (2DEG). Two discernible CR peaks, originating from spin-conserved transitions between adjacent sets of spin-split Landau states, are observed at a magnetic field as low as 4.4 T. The observed doublet features in the vicinity of even and odd integer filling factors are attributed to the linear dependence of the g factor and effective mass on the electron energy, respectively. In addition, our data show that the g factor of a 2DEG has a smaller energy dependence than that of bulk electrons.