Aymeric Ramiere

Researcher in nanoscale heat transfer

Research projects

My research area is nanoscale heat conduction. More specifically, I study the impact of the surface roughness and the nanostructure geometry on the propagation of heat inside solids or at the interface between two materials.

Very low temperatures give access to intersting features of heat propagation such as ballisticty and diffraction which are usually not observable above a few degree Kelvins in materials with patterns larger than tens of nanomaters.

The applications of this fundamental research are to improve energy harvesting with thermoelectric materials and control the drection of heat propagation in nanostructured materials.

Finally, understand heat propagation at low temperature in materials with ten-nanometer-size patterns today is a key to control heat in devices with smaller dimensions at room temperature which should be available in the near future.

Thermal boundary resistance

The origin of the discontinuity of temperature at the interface solid/liquid has remained unexplained for the last 75 years. Our measurements reveal the scattering resonant mechanism solving this mystery.

Heat guiding in phononic nanostructures

The ballisticity of phonons at low temperature suggest the possibility to control the heat flux direction by nanopatterning. We demonstrate this effect by combining Monte Carlo simulations and time-domain thermoreflectance measurements.

Spectral filtering of phonons

Interactions of phonons at rough boundaries is strongly frequency dependent. Monte Carlo simulations show that spectral transmission of phonon can be shaped by controlling the surface roughness.

Dominant phonon wavelength

The general behavior of heat transport can be extracted from the dominant phonon wavelength. We extended the original theory for a single heat reservoir to the situation with two reservoirs and demonstrate a blueshift effect.