Nanotube heat conductors under tensile strain: Reducing the three-phonon scattering strength of acoustic phonons

摘要: Acoustic phonons play a special role in lattice heat transport, and confining these low-energy modes low-dimensional materials may enable nontrivial transport phenomena. By applying lowest-order anharmonic perturbation theory to an atomistic model of carbon nanotube, we investigate numerically analytically the spectrum three-phonon scattering channels which at least one phonon is low energy. Our calculations show that acoustic longitudinal (LA), flexural (FA), twisting (TW) nanotubes exhibit distinct dissipative behavior long-wavelength limit, $|k| \rightarrow 0$, manifests itself rates scale as $\Gamma_{\rm{LA}}\sim |k|^{-1/2}$, $\Gamma_{\rm{FA}}\sim k^0$, $\Gamma_{\rm{TW}}\sim |k|^{1/2}$. These scaling relations are consequence harmonic approximation critically depend on condition tubes free mechanical stress. In this regard, small amounts tensile strain $\epsilon$ reduce strength scattering, resulting strain-modulated that, obey $\Gamma \sim \epsilon^{r} |k|^{s}$ with $r\leq 0$ $s\geq 1$, irrespectively mode polarization. Under single-mode relaxation time linearized Peierls-Boltzmann equation (PBE), long-tube limit thermal conductivity stress-free stretched tube configurations can be unambiguously characterized. Going beyond approximations, analytical results obtained present study help benchmark numerical routines aim deriving from exact solution PBE.