Electrical transport in rings of single-wall nanotubes: One-dimensional localization

We report low-temperature magnetoresistance (MR) measurements on rings of s ingle-wall carbon nanotubes. Negative MR characteristic of weak one-dimensi onal localization is clearly observed from 3.0 to 60 K, and the coherence l ength L-phi, is obtained as a function of temperature. The dominant dephasi ng mechanism is identified as electron-electron scattering. Below 1 K, we o bserve a transition from weak to st,strong localization, and below 0.7 K a weak antilocalization is induced by spin-orbit scattering.