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 (2DEG's) which were formed in two GaAs quantum wells and separated by a thin A lxGa1-xAs barrier. The degree of wave-function hybridization, along wi th the effect of a magnetic field parallel to the plane of the electro n gas, have been investigated near both the quantum and semiclassical limits, corresponding to low and high filling factors, respectively. N ear the quantum regime, the CR transitions in the presence of a small parallel field reveal anticrossing between the Landau levels associate d with different hybridized subbands. The energies and intensities of these transitions change with front gate bias, yielding information on the bias dependence of the wave-function hybridization and the subban d energy splitting. Close to the semiclassical limit and with strong p arallel magnetic fields, two CR peaks are observed. The corresponding cyclotron masses are compared to those expected for noncircular Fermi contours created by anticrossing of the parabolic dispersion curves as sociated with the coupled 2DEG's. Experimental results in both limits are discussed in the light of predictions from self-consistent solutio ns of Poisson's and Schroedinger's equations.