Edge States and Magnetism in Carbon Nanotubes with Line Defects

We apply first-principles calculations to investigate the interplay between electronic and magnetic properties of carbon nanotubes with line defects. We consider three types of defects: lines of C—O—C epoxy groups, and defects resulting from the substitution of the oxygen atoms by CH₂ or C₂H₄ divalent radicals. We find that the line defects behave as pairs of coupled graphene edge states, and a variety of electronic and magnetic ground states is predicted as a function of defect type, nanotube diameter, and a possibly applied transverse electric field.