▎ 摘　　要

Recent theoretical and experimental works on carbon nanotubes and graphene samples have revealed that spin-orbit interactions, though customarily ignored in carbon-based materials, are more important and complex than it was thought. We study the intrinsic spin-orbit coupling effects on graphene nanoribbons, both flat and bent. Calculations are performed within the tight-binding model with the inclusion of a four-orbital basis set; thereby the full symmetry of the honeycomb lattice and the hybridization of sigma and pi bands are considered. In addition to the zero-energy pi-edge states, sigma-derived edge states are found for the three investigated ribbon geometries. The sigma states are also spin filtered and localized at the boundaries of the ribbons. The calculated spin-orbit splittings are larger for the sigma - than for the pi-derived edge states. Due to this enhancement, spin-orbit splittings of the sigma states reach values of the order of a few Kelvin. These spin-filtered edge states are robust under sigma-pi hybridization and curvature effects.