Tunable heat conduction through coupled Fermi-Pasta-Ulam chains

Abstract

We conduct a study on heat conduction through coupled Fermi-Pasta-Ulam (FPU) chains by using classical molecular dynamics simulations. Our attention is dedicated to showing how the phonon transport is affected by the interchain coupling. It has been well accepted that the heat conduction could be impeded by the interchain interaction due to the interface phonon scattering. However, recent theoretical and experimental studies suggest that the thermal conductivity of nanoscale materials can be counterintuitively enhanced by the interaction with the substrate. In the present paper, by consecutively varying the interchain coupling intensity, we observed both enhancement and suppression of thermal transport through the coupled FPU chains. For weak interchain couplings, it is found that the heat flux increases with the coupling intensity, whereas in the case of strong interchain couplings, the energy transport is found to be suppressed by the interchain interaction. Based on the phonon spectral energy density method, we attribute the enhancement of the energy transport to the excited phonon modes (in addition to the intrinsic phonon modes), while the upward shift of the high-frequency phonon branch and the interface phonon-phonon scattering account for the suppressed heat conduction.

Enhanced energy transport owing to nonlinear interface interaction

“…These tubes, layers, or ribbons usually interact with each other through van der Waals (vdW) interactions. In order to understand the role of interface nonlinearity in heat transfer of a nanostructured material, we start with a coupled 1D FK chain model as a simplified working bench of the coupled nanostructures since the FK chains are widely used to depict the real material in condensed-matter physics and nonlinear physics 25 30 31 40 41 42 . The heat transfer along two identical FK chains bundled by vdW interaction is simulated to reveal the energy transport of coupled nanostructures.…”

“…Particularly, if , the interface is pure nonlinear. It is noted that the motion of the particles is restricted in the x direction, so only the inter-chain interaction in the x direction is considered in this model 25 31 . Here the thermostats temperatures of the two ends of each chain are set to be and .…”

“…When β increases further, an inverse relationship between the heat flux and β is clearly exhibited, i.e., heat conduction is suppressed by the strong nonlinear interfacial coupling, which is similar to the results obtained in ref. 31 . To accurately estimate the thermal conductivity of the system, we need to know the accurate temperature gradient.…”

“…Sun et al reported that the thermal transport of a FK chain-bundle can be enhanced by strong interchain Lennard-Jones (LJ) couplings 30 . However, our recent numerical results show that the energy transport in coupled chains is suppressed by strong linear inter-chain interactions 31 . Nevertheless, for strong LJ couplings, the phonon scattering arising from the nonlinear inter-chain interaction is expected to play a dominant role and suppresses the heat conduction.…”

“…It is also reported that the coupling of thermal materials to substrates counterintuitively enhances the thermal conductivity through double-wall nanotubes 25 , supported graphene on substrate 26 , double-layer graphene sheets 27 , supported silicene structures 28 and β -sheet crystals of spider silk protein 29 . To get a more in-depth understanding on the important role of the interface coupling in the heat transfer through these nanostructures, the coupled nonlinear lattices, i.e., coupled Frenkel-Kontorova (FK) lattices 30 and Fermi-Pasta-Ulam (FPU) lattices 25 31 , have been employed as a simplified working models of real systems. Sun et al reported that the thermal transport of a FK chain-bundle can be enhanced by strong interchain Lennard-Jones (LJ) couplings 30 .…”