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

摘要

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.