Specular Acoustic Vibrational Wave Transmissions with the Presence of Phononic Bandgaps

Since nanomaterials have high surface/volume ratio, vibrational wave transmission at solid interfaces is of great importance in nanotechnologies and have been extensively examined for the past 30 years. However, studies were limited to material systems that have continuous vibrational density of states overlap in the acoustic branches. This does not fully represent nanostructured devices, where the vibrational properties exhibit gaps due to phononic behaviors. In this research, we utilize superlattices, the simplest form of phononic structure, to create such situations and investigate the resulting phonon transmissions. We demonstrate how mini-gap formation in phononic structures can affect specular phonon transmissions and discuss its implications on the transmission mechanism of acoustic phonons through nanostructures.