Heat conduction of multilayer nanostructures with consideration of coherent and incoherent phonon transport

We report a theoretical investigation of coherent-to-incoherent heat conduction in multilayer nanostructures. In the coherent regime where the phonon motion is quasi-harmonic, the elastic continuum model gives accurate cross-plane thermal conductivity predictions of upper limits and demonstrates that the coherent transport is the result of the interplay between intrinsic wave effects. As the temperature or system size increases, the phonon dephasing scattering results in the deviation of thermal conductivity from the coherent-limit calculation. By further introducing the incoherence of phonons, we reproduce the classical minimum thermal conductivity, indicating the feasibility of extending the pure wave model into the wave-particle crossing regime.