  We report 13C nuclear magnetic resonance measurements on single wall carbon
nanotube (SWCNT) bundles. The temperature dependence of the nuclear
spin-lattice relaxation rate, 1/T1, exhibits a power-law variation, as expected
for a Tomonage-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 behavior is observed suggests that SWCNT is so
far the best realization of a one-dimensional quantum metal.
