Analysis of the low-temperature specific heat of multiwalled carbon nanotubes and carbon nanotube ropes

We analyze specific-heat measurements in the temperature range 1<T<200 K fo r two types of carbon nanotube samples: multiwalled tubes and ropes of sing le-walled tubes. The multiwalled tube sample has a specific-heat not unlike that of graphite, which we maintain is reasonable given the structural sim ilarities between the two materials. In contrast, the low-temperature speci fic-heat data for ropes are surprisingly large in magnitude and have surpri singly strong temperature dependence. We present model calculations that hi ghlight the puzzling nature of these results and then suggest explanations. [S0163-1829(99)00129-0].