  The engineering of phononic resonances in ferroelectric structures appears as
a new knob in the design and realization of novel multifunctional devices. In
this work we experimentally study phononic resonators based on 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, the time and spatial beatings resulting from the coupling of two
different hybrid nanocavities forming an acoustic molecule, and the direct
measurement of Bloch-like oscillations of acoustic phonons in a system formed
by 10 coupled resonators. By means of coherent phonon generation techniques we
study the phonon dynamics directly in the time-domain. The metallic SrRuO3
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 tool for the study of complex
wave localization phenomena at the nanoscale.
