Infrared studies of combined resonance in n-type InSb

The combined resonance absorption line involving a change in both Landau (L) and spin (S) quantum numbers (ΔL=1; ΔS=-1) has been studied in several samples of n-type InSb having carrier concentrations between 1014 and 1016 cm-3. Experiments were performed at liquid-nitrogen and liquid-helium temperatures in magnetic fields between 10 and 100 kG. Measurements of the integrated absorption of this line as a function of magnetic field and carrier concentration are compared with calculations based on the non-parabolicity and inversion-asymmetry mechanisms. Results are in good agreement with the predictions of the nonparabolicity mechanism, indicating that this is the primary mechanism allowing such transitions in InSb. The observed combined resonance transition in conjunction with spin-up and spin-down cyclotron resonance measurements have yielded the g values of the L=0 and L=1 Landau levels over a wide range of magnetic fields. None of the inversion-asymmetry-allowed transitions were observed. From this negative result, an upper bound is placed on the inversion-asymmetry parameter δ0.