Cyclotron resonance studies of strongly coupled double quantum wells in tilted magnetic fields near the quantum and semi-classical limits

Far-infrared cyclotron resonance (CR) spectroscopy has been 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 wave function hybridisation, along with the effect of a magnetic field parallel to the plane of the electron gas, have been investigated near both the quantum and semi-classical limits, corresponding to low and high filling factors, respectively. 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 bias, yielding information on the bias dependence of the wave function hybridisation and the subband energy splitting. Near the semi-classical limit and with strong parallel magnetic fields, two CR peaks are 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. Experimental results in both limits are compared with predictions from self-consistent solutions of Poisson's and Schrodinger's equations. (C) 1998 Elsevier Science B.V. All rights reserved.