Figure 6. Contours of constant coupling Jω between two spin-guides acting as a directional coupler, as a function of the potential depth and the separation between the guides.
The coupling strength decreases with increasing depth as well as with increasing separation between guides. At small currents, the modes become unbound. The thumbnails on the top and right sides show cross sections of the magnetic field perpendicular to the guiding direction, to illustrate the relative change in the shape of the potential along both axes.