Transport characteristics of a window-coupled quantum-wire system in nonuniform magnetic fields

This work reports on a theoretical investigation of magnetotransport in a window-coupled quantum-wire system using a scattering matrix method. The system consists of two parallel quantum channels with magnetic fields of the same strength applied and a ballistic coupling window without being applied with magnetic field. Two magnetic-field configurations in which the magnetic fields have been applied both parallelly and antiparallelly are considered. Various transmissions and two typical four-terminal resistances (a Hall and a longitudinal resistance) are calculated. Predicted for the system in both magnetic field configurations are a general enhancement of the wave coupling in the low strength region of the magnetic fields and sharp resonant and antiresonant peaks in the transmissions through the coupling window in the strong strength region. We attribute this enhancement to the suppression of backscattering of electron waves at the interfaces between the coupling window and the quantum channels and these peaks to resonant transmissions and resonant reflections via localized states formed in the coupling window. The calculated Hall and longitudinal resistances show different behaviors in the low strength region of the magnetic fields, while in the strong strength region they, at a given number of open modes in the quantum channels, depend only on a single nonzero transmission through the coupling window. The electron charge density and electron flux density at selective strengths of the applied magnetic fields are calculated and plotted in order to illustrate the physics associated with the predicted transport properties of the system. (C) 1998 American Institute of Physics. [S0021-8979(98)01816-7].