Acoustic confinement phenomena in oxide multifunctional nanophononic devices

Engineering of phononic resonances in ferroelectric structures is a new knob to realize novel multifunctional devices. Here we show the possibility of predictively designing and fabricating phononic nanoresonators utilizing combinations of MBE-grown insulating (BaTiO3, SrTiO3) and metallic (SrRuO3) oxides. We experimentally demonstrate the confinement of acoustic waves in the 100-GHz frequency range in a phonon nanocavity, and the the time and spatial beatings resulting from the coupling of two different hybrid nanocavities forming an acoustic molecule. Additionally, the direct measurement of Bloch-like oscillations of acoustic phonons is observed in a system formed by ten coupled resonators. Utilizing coherent phonon generation techniques, we study phonon dynamics directly in the time domain. The metallic SrRuO3 layer introduces a local phonon generator and transducer that allows for the spatial, spectral, and time-domain monitoring of the complex generated waves. Our results introduce ferroelectric cavity systems as a new realm for the study of complex wave localization phenomena at the nanoscale. These systems can be successfully designed and conceived using state of the art growth techniques that combine perovskite oxides possessing multifunctional properties.