The far-infrared magneto-optical response of strongly coupled 2DEGs near the quantum and semi-classical limits

Abstract

Far-infrared cyclotron resonance (CR) spectroscopy was used to study a pair of strongly coupled two-dimensional electron gases (2DEGs) formed in two GaAs quantum wells separated by a thin AlGaAs barrier. The degree of wavefunction hybridisation, along with the effect of a magnetic field parallel to the plane of the electron gas, were investigated near both the quantum and semi-classical limits, corresponding to low and high filling factors, respectively. Results in both limits are compared with predictions from self-consistent solutions of the Poisson and Schrödinger equations. Near the quantum regime, the CR transitions in a small parallel field reveal anticrossing between the Landau levels associated with different hybridised subbands. The energies and intensities of these transitions change with front gate voltage, yielding information on the bias dependence of the wavefunction hybridisation and the subband energy splitting. Near the semi-classical limit and with strong parallel magnetic fields, two CR peaks were observed. The corresponding cyclotron masses are compared to those expected for non-circular Fermi contours created by anticrossing of the parabolic dispersion curves associated with the coupled 2DEGs.