Ballistic-electron transport through a coupled-quantum-wire system

We study the ballistic-transport properties of a coupled-quantum-wire system where two wires are connected by a coupling region. The region is gated and permits, therefore, a coupling which can be varied. In particular, we evaluate the transmission and reflection coefficients for a variety of system parameters. By considering the scattering at the interaction region between the quantum wires, we find that this system behaves as an electron-waveguide coupler, similar to that of an optical coupler. Periodic switching of the electron wave between the quantum wires is observed. Complete electron transfer occurs at a transfer length as short as 400 Å, which is much smaller than the phase-breaking length, implying that this system is experimentally realizable. We also present a detailed study of the quantum bound states in such an open system. Finally, the Büttiker resistance of this four-terminal system is presented.