Collective Phenomena in Multiwall Carbon Nanotubes

Collective phenomena due to persistent currents in carbon multiwall nanotubes are studied. The formula for persistent currents minimising free energy and conditions for the stability of persistent currents in multiwall nanotubes in magnetic field are derived. Numerical calculations performed show the possibility of obtaining spontaneous currents in two optimal configurations: undoped armchair-only multiwall nanotubes up to 0.01 K, and zig-zag-chiral-chiral-zig-zag multiwall nanotubes doped to -3.033 eV up to about 1 K. The latter configuration may exhibit also the diamagnetic expulsion of magnetic field, which according to our calculations can reach 20% of the external flux.