EDGE EXCITATIONS AND THE FRACTIONAL QUANTUM HALL-EFFECT IN DOUBLE QUANTUM-WELLS

The structure of the edge excitations of a quantum Hall droplet, confined in a double quantum well, is studied using a generalized version of the Wen-Stone chiral boson action. As the interwell tunneling t is increased, one finds a "metal-insulator" transition from a phase where the optic edge mode is ungapped to a phase where the optic mode is gapped. The large-t phase exhibits edge quasiexcitons whose charge is half that of a quasiparticle-quasihole bound state. The critical behavior of the conductances, the exciton gap, and the excitonic order parameter is discussed.