We observe electron spin resonance using FIR laser spectroscopy in symmetric and asymmetric InSb quantum wells over a wide range of magnetic field and the Landau level index. The behavior of the asymmetric wells at low magnetic fields with g-factors far in excess of the bulk g-factor of InSb is due to spin splitting at zero magnetic field. Asymmetry-induced shifts in the spin resonance at high fields depend on the Landau level index as predicted by the Bychkov-Rashba model. In an extension of this work, we plan to compare samples where the asymmetry in the confinement potential is due to differing Al concentrations in the barriers on either side of the quantum well to samples with asymmetric doping which were studied in this work.

The alpha values measured in this work (1.5 x 10-9 eVcm) are among the largest reported as would be expected for a material like InSb with a large bulk g-factor. Recently, in gated InAs samples [61] alpha values ranging from 2 x 10-9 to 4 x 10-9 eV cm have been measured which suggest that we can achieve even larger alpha in InSb quantum wells. We are extending our spin resonance studies to gated samples. These should give us the ability to study the spin resonance in the absence of any applied magnetic field.

Our cyclotron resonance experimental results are in good agreement with our theoretical model. The values of the effective mass show the expected nonparabolicity behavior. We observed spin resolved cyclotron resonance in the high mobility samples with a rather unexpected amplitude pattern at 70.6 mum which might be a result of deviation from the Kohn theorem. More experiments using FTIR are required to understand the spin resolved cyclotron resonance in InSb.

The goal of this work was to study the band structure and spin properties of the InSb quantum wells experimentally. Many new observations resulted such as spin resolved cyclotron resonance and zero field spin splitting in InSb quantum wells.