  We propose a new orbital controlled model to explain the gate field induced
switching of current in a semiconducting PbS-nanowire junction. A single
particle scattering formalism in conjunction with a posteriori density
functional approach involving hybrid functional is used to study the electronic
current; both first and higher order Stark effects are explicitly treated in
our model. Our calculation reveals that after a threshold gate-voltage, orbital
mixing produces p-components at the S atoms in the participating orbitals. This
results in an inter-layer orbital interaction that allows electron to
delocalize along the channel axis. As a consequence a higher conductance state
is found. A similar feature is also found in a PbSe nanowire junction, which
suggests that this model can be used universally to explain the gate field
induced switching of current in lead-chalcogenide nanowire junctions.
