Incidence of the Tomonaga-Luttinger liquid state on the NMR spin-lattice relaxation in carbon nanotubes

We report (13)C nuclear magnetic resonance measurements on (13)C-enriched single-wall carbon nanotube (SWCNT) bundles. The temperature dependence of the nuclear spin-lattice relaxation rate, 1/T(1), exhibits a power law variation, as expected for a Tomonaga-Luttinger liquid (TLL). The observed exponent is smaller than that expected for the two-band TLL model. A departure from the power law is observed only at low T, where thermal and electronic Zeeman energy merge. Extrapolation to zero magnetic field indicates gapless spin excitations. The wide T range on which power law behaviour is observed suggests that SWCNT is so far the best realization of a one-dimensional quantum metal. Copyright (C) EPLA, 2010