Spin Resolved Cyclotron Resonance and Magneto-absorption in InSb Multiple Quantum Wells

We present calculations of the spin-dependent cyclotron resonance and magneto-absorption spectra in strained, narrow gap AlInSb/InSb multiple quantum wells. Our calculations are based on the 8-band Pidgeon-Brown model generalized to including the effects of the confinement potential and pseudomorphic strain. Optical properties are calculated within the golden rule approximation and compared with experiments. The large g-factors allow one to spin-resolve the transitions at modest magnetic fields ($<$10T). In the magneto-absorption, we see spin-split transitions and identify both bright and dark transitions in agreement with experiment. For cyclotron resonance, we see not only spin-resolved anticrossings between Landau levels with the same spin, but also anticrossings between levels of opposite spin. These opposite spin anticrossings result from spin-orbit coupling and the resonance-enhanced mixing of the second Landau level of the ground state subband and the lowest Landau level of the first excited state of opposite spin.