Cyclotron and spin resonance in electron inversion layers on InSb

Cyclotron and electron spin resonance in inversion layers on InSb are studied by far-infrared laser and Fourier-transform spectroscopy. For the interpretation of the optical spectra the occupancies of electric subbands in magnetic fields have been derived from Shubnikov--de Haas measurements. Cyclotron masses and effective Land\'e g factors are given as a function of inversion electron density and of cyclotron energy, i.e., magnetic field. We emphasize nonparabolic and polaron effects and discuss the experimental results with a three-level model in magnetic fields. Since until present no self-consistent calculations in the presence of magnetic fields exist for InSb, we employ the triangular-well approximation for the electrostatic surface potential to obtain a qualitative description of our experiments. At weak magnetic fields good quantitative agreement is obtained between experiments and existing Hartree calculations performed in the absence of magnetic fields.