Scattering-mediated transmission and reflection of high-frequency phonons at a nonideal solid-solid interface

We propose a mechanism by which energy transfer by phonons between two solids may be modified by interface irregularity, so-called scattering-mediated transmission. The interface region is modeled as a thin layer of varying thickness sandwiched between irregular boundaries, having density and elastic constants different to those of the bulk on either side. We find that the process gives rise to a contribution to phonon transmission that varies as ω⁴ at low frequencies, switching to ω² at higher frequencies. The frequency at which the exponent changes, and also that at which the process becomes comparable with coherent transmission, depends on the length scale of the interface irregularity. Numerical estimates confirm that the process is likely to make a major contribution in situations of current interest.