The effects of intrinsic spin-orbit and Coulomb interactions on low-energy
properties of finite width graphene armchair ribbons are studied by means of a
Dirac Hamiltonian. It is shown that metallic states subsist in the presence of
intrinsic spin-orbit interactions as spin-filtered edge states, in contrast
with the insulating behavior predicted for graphene planes. A charge-gap opens
due to Coulomb interactions in neutral ribbons, that vanishes as Δ∼1/W, with a gapless spin sector. Weak intrinsic spin-orbit interactions do
not change the insulating behavior. Explicit expressions for the
width-dependent gap and various correlation functions are presented.Comment: Will appear in PR