Large positive magnetic susceptibility of nanotube torus

Abstract

We calculate the magnetic moment caused by the persistent currents in polygonal carbon nanotube tori by the tight binding model. The polygonal CNT tori are formed by introducing heptagonal and pentagonal defects along the inner hole and outer fringe, respectively. We found a new type of large paramagnetic persistent current caused by the semi-metallic band structures of the periodic CNT junction. It is contrasted with the persistent current originated from the metallic band structure. In spite of diamagnetism of the graphite, this paramagnetism is caused by not only the magnetic flux in the inner hole (AB flux) but also the magnetic flux directly penetrating the graphite plane (direct flux). This magnetic moment is close to that calculated with only Aharonov Bohm effect where the direct flux is included in the AB flux.