Phonon-interference Resonance Effects of Nanoparticles Embedded in a Matrix

We report an unambiguous phonon resonance effect originating from germanium nanoparticles embedded in silicon matrix. Our approach features the combination of phonon wave-packet method with atomistic dynamics and finite element method rooted in continuum theory. We find multimodal phonon resonance, caused by destructive interference of coherent lattice waves propagating through and around the nanoparticle, gives rise to significantly sharp transmittance dips, blocking phonon transport in the low-end frequency range that is hardly diminished by other nanostructures. The resonance is sensitive to the phonon coherent length, where the finiteness of wave packet width weakens the transmittance dip even when the coherent length is larger than the particle size. Further strengthening of transmittance dips is achieved by arraying multiple nanoparticles that leads to collective resonant mode. Finally, atomistic Green's function demonstrates that these resonance effects can significantly reduce thermal conductance in the low-end frequency range.