QUANTUM HALL-EFFECT IN ASYMMETRIC DOUBLE-QUANTUM-WELL SYSTEMS

We have experimentally determined the phase diagram of the quantum Hal l effect in asymmetric double quantum well heterostructures. The charg e redistribution induced by a crossing of the Landau levels of the two -dimensional electron gases is strongly regulated by the electrons in the excited subband. The self-consistency of the potential imposes a r eduction in the charge transfer when the layer separation is large, Fo r a range of electron densities beyond the population threshold of the excited subband, subpeaks are generated from the resistance peaks due to the ground subband. The split-off peaks grow larger in amplitude t o become comparable with the contribution from the ground subband when the electron density in the excited subband increases. The relocation of the electrons between the subbands leads to a hybridization of the behaviour in each layer. The Hartree potential is found to yield a me tastability of the electron state with the assistance of the discrete nature of the density of states in high magnetic fields.