Coupling site controlled spin transport through the graphene nanoribbon junction

A new type of nano-junctions based on Zigzag graphene nanoribbons (ZGNRs) has been proposed and investigated by first-principles calculations. The results show that large spin polarization of currents would be achieved when the junctions adopted the configuration that two ZGNR leads coupled each other along one edge. By virtue of spatial separation of the two spin edge states, only one spin channel is opened in those junctions at certain energy range, and spin polarized currents will be produced under a low bias. No more efforts are required to change ZGNR from the antiferromagnetic (AFM) ground states to the ferromagnetic (FM) states. Specially, this feature is stable, by changing the width of ZGNRs, modifying the edge morphology, and varying dihedral angle between two ZGNRs, spin polarization of currents are still observed. Our findings indicate that this approach is simple and efficient for spintronics design.