Impact of four-phonon scattering on thermal transport in carbon nanotubes

The thermal transport properties of single-wall carbon nanotubes (SWCNTs) are reinvestigated using the iterative solution of the Boltzmann transport equation by including four-phonon scattering. Using only three-phonon scattering, the flexural and twisted phonon modes are found to remain nonscattered via Umklapp processes. However, with four-phonon scattering, while longitudinal modes remain unaffected, the transverse modes undergo Umklapp scattering. The predicted thermal conductivity of SWCNTs using both three- and four-phonon scatterings is 4000 W/m-K at 300 K, and stays highest amongst all known materials.