  We present calculations of the quasiparticle energies and band gaps of
graphene nanoribbons (GNRs) carried out using a first-principles many-electron
Green's function approach within the GW approximation. Because of the
quasi-one-dimension nature of a GNR, electron-electron interaction effects due
to the enhanced screened Coulomb interaction and confinement geometry greatly
influence the quasiparticle band gap. Compared with previous tight-binding and
density functional theory studies, our calculated quasiparticle band gaps show
significant self-energy corrections for both armchair and zigzag GNRs, in the
range of 0.5-3.0 eV for ribbons of width 2.4-0.4 nm. The quasiparticle band
gaps found here suggest that use of GNRs for electronic device components in
ambient conditions may be viable.
