Using magnetic fields and band gap engineering to achieve robust spin filtering in finite quantum dot arrays

In periodic quantum dot arrays, conductance can be modulated by exploiting band gap effects. Since the backscattering effects that produce some of the band gaps are comparatively strong, an open array with as little as three dots can be utilized to achieve zero transmission. Utilizing Zeeman-splitting, one can create a situation where, by the shifting the gaps for the individual spins, one can achieve nearly 100% spin polarization. The energy scales over which this polarization is achieved depends on the size of the band gaps. Thus, the effect can be enhanced further by band gap engineering, picking the structure that maximizes the size of the gaps for a given Fermi energy and field.