CYCLOTRON-RESONANCE STUDIES OF STRONGLY COUPLED DOUBLE-QUANTUM WELLS IN TILTED MAGNETIC-FIELDS NEAR THE QUANTUM AND SEMICLASSICAL LIMITS

Far-infrared cyclotron resonance (CR) spectroscopy has been used to st udy a pair of strongly coupled two-dimensional electron gases (2DEGs) formed in two GaAs quantum wells separated by a thin AlGaAs barrier. T he degree of wave function hybridisation, along with the effect of a m agnetic field parallel to the plane of the electron gas, have been inv estigated near both the quantum and semi-classical limits, correspondi ng to low and high filling factors, respectively. Near the quantum reg ime, the CR transitions in a small parallel field reveal anticrossing between the Landau levels associated with different hybridised subband s. The energies and intensities of these transitions change with front gate bias, yielding information on the bias dependence of the wave fu nction hybridisation and the subband energy splitting. Near the semi-c lassical 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 t he parabolic dispersion curves associated with the coupled 2DEGs. Expe rimental results in both limits are compared with predictions from sel f-consistent solutions of Poisson's and Schrodinger's equations. (C) 1 998 Elsevier Science B.V. All rights reserved.