AVS 50th International Symposium
    Nanotubes Wednesday Sessions
       Session NT-WeP

Paper NT-WeP17
Large Paramagnetic Susceptibility and Field Induced Persistent Current for Carbon Nanotube Tori

Wednesday, November 5, 2003, 11:00 am, Room Hall A-C

Session: Poster Session
Presenter: R. Tamura, Shizuoka University, Japan
Authors: R. Tamura, Shizuoka University, Japan
M. Tsukada, University of Tokyo, Japan
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Magnetic susceptibilities have been calculated for a number of Carbon nanotube (CNT) tori with the tight binding model. We found large paramagnetic susceptibility which cannot be expected when the system size is larger than the order of the nanoscale. The CNT torus with six-fold rotational symmetry is composed of six unit cells. The unit cell is an armchair nanotube with two pentagonal defects and two heptagonal defects. Direction of the tube axis is changed by sixty degrees by the defects. When this unit cell is repeated periodically, on the other hand, the helical CNT is formed.@footnote 1@ The energy levels of the CNT torus can be obtained from the dispersion relation of the helical CNT, E(k), by choosing only the discrete wave number k=@pi@j/3 with an integer j. The magnetic field penetrating the torus surface change the dispersion relation E(k), while magnetic field through the hole shift the discrete wave number due to the AB effect. When the helical CNT is semi-metallic, it is possible that LUMO band bottom at k=0 is lower than the HOMO band over some k region.@footnote 2@ In that case, electron at the HOMO band makes a transition to the k=0 LUMO sate so that number of occupied levels with positive k is different from that with negative k. This causes the persistent current and large positive magnetic susceptibility, in spite of large negative magnetic susceptibility of graphite. @FootnoteText@@footnote 1@R. Tamura and M. Tsukada,Journal of Physical Society of Japan, Vol. 68, pp.910-922 (1999)@footnote 2@K. Akagi, R. Tamura, M. Tsukada, S. Itoh, and S. Ihara, Phys. Rev. B,Vol. 53, pp.2114-2120 (1996) .