1 6 O ct 2 00 1 Electron - electron interaction in multiwall carbon nanotubes ⋆

Magnetic susceptibility χ of pristine and brominated arc-produced sample of multi-wall carbon nanotubes was measured from 4.2 to 400 K. An additional contribution ∆χ(T) to diamagnetic susceptibility χ(T) of carbon nanotubes was found at T < 50 K for both samples. It is shown that ∆χ(T) are dominated by quantum correction to χ for interaction electrons (interaction effects-IE). The IE shows a crossover from two-dimensional to three-dimensional at B = 5.5 T. The effective interaction between electrons for interior layers of nanotubes are repulsion and the electron-electron interaction λ c was estimated to be λ c ∼ 0.26. From the time of discovery nanotubes one of the most important problems is the possibility of a superconducting state in them. In a series of experiments were observed the effects which indicate on its existence. There is supercur-rents through single-walled carbon nanotubes [1], persistent currents and magnetic flux trapping [2]. As is known the nature of a superconducting state is the electron-electron interaction (Namely-attraction between electrons). On the other hand electron-electron interaction is exhibited in electronic transport properties of conductors in normal state-so-called quantum interference effects-interaction effects (IE) [3,4]. IE are connected with the correction