Imaging the local flow of heat and phonons

Efficient heat management is of paramount importance for modern-day electronics to ensure optimal performance and energy consumption.

While Fourier's two-century-old macroscopic model for heat diffusion has served as a valuable tool, in particular for homogeneous solids at room temperature, it does not hold on short time and length scales.

Notably, the model assumes that an abrupt and localized temperature perturbation propagates instantly everywhere in the rest of the material.This project aims to visualize the breakdown of the Fourier's law, paving the way for the development of a more physically satisfying model of heat propagation.

My investigation will focus on a specific and very illustrative non-Fourier transport regime that has recently attracted considerable interest in the scientific community: the viscous hydrodynamic regime.

To achieve this, I will design and construct a highly sensitive, and spatially resolved thermometer, capable of probing material surfaces with an exceptional resolution to resolve heat propagation at the nanoscale. This tool is a SQUID-on-tip (SOT).

I will carefully scan materials known to exhibit this phenomenon at different scales and play with geometries to enhance or attenuate its effects.

By comparing the temperature maps obtained in these regimes with predictions from recent theoretical propositions, I will directly test these models.

This project will illuminate the underlying microscopic mechanisms responsible for heat transport, offering crucial insights into the intricate nature of heat propagation in materials at the nanoscale.THERMOSCOPY represents a groundbreaking initiative that will serve as a stepping stone towards the formulation of a comprehensive physical model for heat propagation in solids beyond the Fourier equation.

This will impact the design of future more energy efficient materials.