Magnetotransport of carbon nanotubes: magnetic-field-induced metal-insulator transition

We have measured magnetotransport of an individual multi-walled carbon nano tube. Though the resistance without magnetic field increases with decreasin g temperature (non-metallic) from room temperature down to 2 K, it becomes metallic below 30 K by applying a magnetic field (H approximate to 4 T) per pendicular to the nanotube axis. The transverse magnetoresistance (TMR) bel ow 30 K decreases with increasing magnetic field, and after reaching minimu m value around 4 T, it increases. On the other hand, under the intense magn etic field above 6 T the TMR does not show continuous increase but tends to be saturated. The results can be explained by the theoretical prediction o f the magnetic-field-induced metal-insulator transition of semiconducting c arbon nanotubes. (C) 2001 Elsevier Science B.V. All rights reserved.