Electronic band structure of carbon nanotube superlattices from first-principles calculations

We report on first-principles calculations for metallic carbon nanotube superlattices N(12,0)/N(6,6) with N=1-4. Although the calculated band structures show a good overall agreement with the results of the simpler tight-binding pi-electron approximation, electron interaction and correlation effects strongly modify some peculiar flatbands, previously found within a tight-binding approach [W. Jaskolski and L. Chico, Phys. Rev. B 71, 155405 (2005)]. In the ab initio approach, these bands are no longer dispersionless, much closer to the Fermi level, and are always nondegenerate, in contrast to former tight-binding results.