Fig. 2

Electronic properties from many-body perturbation theory. a GW (dashed lines) and DFT (solid lines) band structure of the armchair carbon nanotube (3, 3). b Zoom close to the Dirac point K. The momentum q is referenced from K. c Long-range part of electron–hole interaction V(z) along the tube axis according to: DFT (solid line), effective-mass model (dashed line). Inset: interaction V(q) in momentum space. V is integrated over the mesh of the q grid and projected onto the conduction and valence bands shown in panel b, with |q| < 0.09(2π)/a. The graphene lattice constant is a=2.46 Å