Spin-valve effect in a carbon atomic wire

We report a theoretical investigation of the spin-valve effect in an atomic scale system, a carbon chain, generated by the presence of a magnetic field in the device leads. We found that there exists a cutoff energy beyond which the conductance of the device vanishes. This cutoff energy can be critically controlled by the relative orientation of the magnetic fields applied to the leads, so that an atomic scale spin valve can be achieved that switches off electric current when magnetic fields of left and right leads are anti-parallel. The physical origin of this transport behavior is found to be related to the wave-function overlap between the leads and the device scattering region.