Analysis of electron transfer between parallel quantum wires

Coupled quantum wire structures, created by applying various potentials to properly shaped gates, have been recently demonstrated. These experiments indicate that directional couplers for electron waveguides, in which the rate of lateral tunneling is controlled by means of external potentials, can be conceived. Such devices could play an important role as switching elements in future logic circuits based on quantum effects. The exact 3-D numerical simulation of these structures is a formidable problem. However, if we can assume that the variation of the potential along the quantum wires is quasi-adiabatic, the transverse wavefunctions and the potential for each cross-section along the wire can be obtained from independent solutions of 2-D self-consitent problems, for which efficient numerical techniques exist. A quasi 3-D transport model can then be obtained by proper matching of the solutions for the transverse sections. This work describes an adaptation of a recursive Green's function technique, based on the tight-binding formalism, which is suitable for a fast analysis of coupled quantum wires. The transmission probability and the conductance are reported for some representative structures at liquid helium temperature.