Computing coherent phonon lifetimes in layered acoustic cavities.

The confinement of coherent phonons in acoustic cavities can lead to ultrahigh-frequency resonators and may tap into the quantum nature of phonons. Their practicality is linked to the coherent phonon lifetime or the characteristic time scale for the phonons to decohere. This letter presents molecular dynamics simulations to compute lifetimes in cavities formed with layered crystal. In a representative layered crystal, bilayer molybdenum disulfide, the lifetimes are computed as a function of two dominant scattering mechanisms (anharmonic and defect) with phonon-mode-level insight. This computational framework is scalable to cavities with the large chemical and physical complexities found in experiments.