Dimer-covering resonating-valence-bond treatment of single-walled zigzag carbon nanotubes

Single-walled zigzag carbon nanotubes with h hexagons around the carbon nanotube, h ranging from 3 to 19, have been investigated from a resonating-valence-bond point of view. The energies calculated for the undoped h=3n–1 zigzag carbon nanotubes, n integer, suggest that the two lowest-lying phases are degenerate. Therefore, de-confined low-energy topological spin defects would occur. Then, these carbon nanotubes should be conductors, in analogy to polyacethylene. In clear contrast, no such degeneracy is obtained for either, h=3n+1 or h=3n, so bound pairs of topological spin defects are expected to occur in these cases. Our findings provide further insights into electron correlation and exchange effects in carbon nanotubes. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2011