We report on cyclotron resonance ͑CR͒ experiments of high-quality C-doped two-dimensional hole systems in GaAs/AlGaAs quantum wells covering the microwave and far-infrared regimes. At high magnetic field B we observe a strong B dependence of the cyclotron mass m c which can be reproduced by calculations based on a 4 ϫ 4 Luttinger Hamiltonian in the axial approximation. At small B one main and up to three secondary CRs are found, which continuously evolve with smooth magnetic-field dependences. This has not been observed and predicted so far. In the regime of the magnetic quantum limit a further CR is observed, which can be attributed to a transition between Landau levels originating from the two different spin-split heavy-and light-hole subbands.

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The Teraherz (THz) photoresponse of a two-dimensional electron gas in the quantum Hall regime is investigated. We use a sample structure which is topologically equivalent to a Corbino geometry combined with a cross-gate technique. This quasi-Corbino geometry allows us to directly investigate the THz-induced transport between adjacent edge-states, thus avoiding bulk effects. We find a pronounced photo voltage at zero applied bias, which rapidly decreases when an external current bias is applied. The photo voltage and its dependence on the bias current can be described using the model of an illuminated photodiode, resulting from the reconstruction of the Landau bands at the sample edge. Using the sample as a detector in a Fourier transform spectrometer setup, we find a resonant response from which we extract a reduced effective cyclotron mass. The findings support a non-bolometric mechanism of the induced photo voltage and the proposed edge-channel diode model.Comment: 5 pages, 5 eps-figures, accepted for Phys. Rev.

Low temperature magnetotransport measurements and far infrared transmission spectroscopy are reported in molecular beam epitaxial grown twodimensional hole systems confined in strained InAs quantum wells with magnetic impurities in the channel. The interactions of the free holes spin with the magnetic moment of 5/2 provided by manganese features intriguing localization phenomena and anomalies in the Hall and the quantum Hall resistance. In magnetic field dependent far infrared spectroscopy measurements well pronounced cyclotron resonance and an additional resonance are found that indicates an anticrossing with the cyclotron resonance.