Geometric, magnetic and electronic properties of folded graphene nanoribbons

Geometric, magnetic and electronic properties of folded graphene nanoribbons (GNRs) are investigated by first-principles calculations. These properties are mainly dominated by the competition or cooperation among stacking, curvature and edge effects. For the folded zigzag GNRs, the more stable structures are revealed to be AB stackings, while for the armchair types, AA′ stackings are more stable. The interlayer interactions and hybridization of four orbitals lead to smaller energy gaps, anti-crossing bands, and more band-edge states. Specifically, the edge atoms, with the different magnetic environments, in the odd-zAB-stacked folded zigzag GNRs are responsible for the spin-up and spin-down splitting subbands. All folded GNRs are direct-gap semiconductors except that the edge-edge interactions cause the even-zAA-stacked folded zigzag GNRs to exhibit a pair of metallic linear bands. The width-dependent energy gaps in the folded armchair GNRs can be classified into six categories. Furthermore, there exist rich features in density of states, including the form, number, intensity and energy of the special structures.