Correlations, compressibility, and capacitance in double-quantum-well   systems in the quantum Hall regime
  In the quantum Hall regime, electronic correlations in double-layer two-dimensional electron systems are strong because the kinetic energy is quenched by Landau quantization. In this article we point out that these correlations are reflected in the way the partitioning of charge between the two-layers responds to a bias potential. We report on illustrative calculations based on an unrestricted Hartree-Fock approximation which allows for spontaneous inter-layer phase coherence. The possibility of studying inter-layer correlations by capacitive coupling to separately contacted two-dimensional layers is discussed in detail. 
T. Jungwirth (Institute of Physics, Prague) and A.H. MacDonald   (Indiana University)