Closely separated one-dimensional wires: coupled ballistic conduction, wave function hybridization and compressibility investigations

We report the experimental study of a system comprising two parallel quasi-one-dimensional (1D) ballistic wires formed in a GaAs-AlxGa1-xAs double quantum well structure. A unique surface gate geometry allows the device to be tuned smoothly from a configuration comprising a pair of vertically aligned 1D ballistic wires, to a single 1D ballistic wire in either the upper or lower 2DES. We investigate coupled ballistic conduction in two samples with contrasting wire separations (35 and 300 Angstrom). The strongly coupled sample exhibits a cross-over from double to single wire conduction as the number of occupied 1D subbands is reduced. The weakly coupled sample is used to observe directly variations in the compressibility of a single ballistic channel arising from the discrete 1D density of states. (C) 1998 Elsevier Science B.V. All rights reserved.