Effect of intertube coupling on the electronic structure of carbon nanotube ropes

Abstract

We calculate the structural and electronic properties of an ordered “bundle” of (10,10) carbon nanotubes. Our results indicate that intertube coupling causes an additional band dispersion of $\lesssim 0.2\hspace{0.5em}\mathrm{eV}$ and opens up a pseudogap of the same magnitude at $E_F.$ Soft librations at $\nu \approx 12\hspace{0.5em}{\mathrm{cm}}^{-1}$ are predicted to occur below the orientational melting temperature which marks the onset of tube rotations about their axis. Whereas the density of states near $E_F$ increases by 7% due to intertube coupling and by one order of magnitude due to K doping in ${\mathrm{KC}}_8,$ these states do not couple to tube librations.