  The universal features of quantized thermal conductance of carbon nanotubes
(CNTs) are revealed through theoretical analysis based on the Landauer theory
of heat transport. The phonon-derived thermal conductance of semiconducting
CNTs exhibits a universal quantization in the low temperature limit,
independent of the radius or atomic geometry. The temperature dependence
follows a single curve given in terms of temperature scaled by the phonon
energy gap. The thermal conductance of metallic CNTs has an additional
contribution from electronic states, which also exhibits quantized behavior up
to room temperature.
