Nano-phononics is an emerging science that deals with the transport of thermal phonons at small length scales. When a waveguide becomes smaller than the mean free path or the phonon wavelength (ℓ100nm), heat transfer is strongly affected. After a historical introduction to thermal measurements, I'll present the results we've obtained through ultra-sensitive thermal conductance measurements on nano-objects (nanowires, membranes).
These experiments show that the notions of phonon mean free path and dominant wavelength are key to understanding phonon thermal transport below 10K. We demonstrate the possibility of manipulating these phonons by modifying the geometry of thermal conductors. Different geometries have enabled us to show how the thermal conduction of certain nanosystems can be greatly reduced.
The use of these new concepts for nano-engineering phonons at room temperature opens up the possibility of developing new nanostructured materials for thermoelectricity. This opens up prospects for future applications in energy recovery: we will give a few illustrations.
