PROBING THE FERMI SURFACES OF COUPLED DOUBLE-QUANTUM WELLS IN THE PRESENCE OF AN INPLANE MAGNETIC-FIELD

The anticrossing of the dispersion relations of two two-dimensional el ectron gases (2DEGs) in an in-plane magnetic field results in distorte d Fermi surfaces, leading to density of states and effective mass chan ges. We have used two different techniques to probe such changes with both the in-plane field and carrier density being systematically alter ed. The first technique uses a fixed perpendicular field to form Landa u levels. By following the evolution of these Landau levels with in-pl ane field, carrier density and temperature, we are able to determine c hanges in the subband populations and effective masses. The second tec hnique uses a third conducting layer as a detector of chemical potenti al changes in the coupled electron gases. This method also allows the determination of effective mass changes in an in-plane field. Calculat ions of the dispersion curves have been made, illustrating the effect of the parallel held upon subband occupancy and effective mass. These calculations are compared with the experimental data from both methods and are found to be in good agreement.