Strain-induced band modulation of thermal phonons in carbon nanotubes

Abstract

We show that carbon nanopeapods are an ideal artificial superlattice to induce band modulation of thermal phonons. Based on spectral energy density analysis, we found that a periodic deformation in carbon nanotubes induced by fullerene encapsulation leads to zone folding of phonon dispersions up to near the maximum frequency. The zone-folding effect gives rise to phonon band gaps caused either by Bragg reflection or mode hybridization, and this reduces group velocity. This was quantified to play the leading role in reduction of thermal conductivity by the fullerene encapsulation. The strain modulation of thermal phonon bands opens a possibility to control material thermal conductivity.