Pure spin current generation with photogalvanic effect in graphene interconnect junctions

We investigate the photovoltaic behaviors of magnetic graphene interconnect junctions, which are constructed by zigzag graphene nanoribbons (ZGNRs), with the aim to produce pure spin current by photogalvanic effect (PGE). Two kinds of interconnect junctions are designed by connecting two 6-ZGNR with a carbon hexagon (C6) and a carbon tetragon (C4), respectively. It is found that zero charge current is produced under irradiation of light in both structures due to the presence of spatial inversion symmetry. Nevertheless, behind the zero charge current, net pure spin current is produced in the structure with a C6, but not in the structure with a C4. This difference originates from their different edge state distribution and different spatial inversion symmetry of the spin density. However, interestingly, local edge pure spin current can be obtained in both structures. More importantly, the pure spin current generation is independent of the photon energy, polarization type or polarization angle, suggesting a robust way of generating pure spin current with PGE and new possibility of graphene’s applications in spintronics.