QUANTUM COHERENT PHENOMENA IN BILAYER QUANTUM HALL SYSTEMS

On the basis of the composite electron picture, we analyze bilayer quantum Hall systems at the Landau level filling factor nu = 1/m with m an odd integer. A composite electron is an electron bound to statistics flux. It is shown that various Josephson phenomena occur, but not for the Meissner effect. A physical. picture of the commensurate-incommensurate phase transition in the magnetic order is described by analogy with the superconductor Josephson junction. Plasmon excitations are analyzed in each phase. The activation energy anomaly which was recently discovered experimentally is accounted for by the change of the plasmon excitations associated with this phase transition.