Low-temperature specific heat of single-wall carbon nanotubes

Previous low-temperature heat capacity measurements down to 2 K give evidence for I-D quantum confinement of SWNT vibrational modes (J. Hone et al., Science 289 (2000) 1730). We extended the data on the same sample down to 0.1 K. A good fit is obtained up to 4 K with C-p = CnT-2 + 0.043T(0.62) + 0.035T(3) mJ/gK, where the T-2 term is from nuclear hyperfine interactions in ferromagnetic impurities and the T-3 term originates from intertube coupling in agreement with Hone et al. The origin of the T-0.62 term is unknown. Comparison with the vibrational density of states from inelastic neutron scattering is made. (C) 2002 Elsevier Science B.V. All rights reserved.