Generating pure spin current in zigzag graphene nanoribbons by a thermal gradient: the effect of edge doping with BN pairs.

Based on density functional theory combined with non-equilibrium Green's function method, we investigate the thermoelectric transport properties of zigzag-edged graphene nanoribbons (ZGNRs) co-doped by two BN pairs at one edge. By applying the co-doping scheme of BN pairs instead of single B and N atoms as reported in literature, the energy of the quasi-bound states gets very close to the Fermi level. Due to the back scattering from the quasi-bound states, transmission valleys appear around the Fermi level, which results in a large transmission slope and Seebeck thermopower for both spin channels. Interestingly, the signs of the Seebeck thermopower of the two spin channels are opposite and the magnitudes are nearly equal, which can be utilized for generating pure spin current with a thermal gradient. More importantly, the thermal spin current is robust against the change of the distance between the two BN pairs and the doping configuration. These findings suggest a fascinating strategy for thermal spin current generation using BN pair co-doping and will be significant for the design of spintronic devices based on graphene nanoribbons. [ABSTRACT FROM AUTHOR]