Electron cyclotron resonance in In1−xMnxAs

We have made the first observation of cyclotron resonance in In1−xMnxAs alloys. Our data unambiguously show that the effective mass of electrons systematically decreases with increasing Mn concentration x. Using an 8-band k·p method, we demonstrate that this mass reduction is a combined effect of (1) a decrease of the band gap and (2) an effective reduction of the momentum matrix element P due to the sp–d hybridization. We also observed a significant mass decrease with decreasing temperature, its temperature coefficient slightly depending on x. The temperature dependent sp–d-interaction-enhanced Landau level spin splitting cannot account for this unusual temperature dependence.