Tackling climate change is one of the most pressing challenges of our modern society and requires researching new refrigeration and renewable energy systems. Performances of all these systems could be significantly improved if they were combined with solid-state thermal switches and diodes. Current strategies that require to nanostructure materials or to operate in the vicinity of a phase transition, lead to thermal switches or thermal diodes with low efficiencies or not suitable for applications where space is limited. Furthermore, once designed, thermal properties of these elements are set and cannot be modified.
My objective is to investigate a fundamentally new mechanism to design compact and efficient thermal switches and diodes. My strategy exploits, in ferroelectric and ferroelastic oxides, the interactions between phonons and spontaneously occurring planar defects known as domain walls. Domain walls can be easily generated, moved, and oriented by application of a small voltage or a small uniaxial pressure, and interact with phonons as defects do. They are thus perfect interfaces to achieve large and reconfigurable anisotropies in thermal conductivities in controlled directions in a fast and reversible way.
In this ambitious project, I develop a novel approach to demonstrate a dynamic heat flow control through (i) the reversible engineering of the density of domain walls in desired directions, and (ii) the development of advanced experimental techniques for in-operando thermal characterizations. My multidisciplinary strategy will unravel the interactions between phonons and domain walls to reach higher thermal conductivity variations, and lead to ground-breaking thermal switches and diodes. These thermal switches and diodes will be compatible with a large range of devices and have an impact in many fields critical for our transition toward a sustainable future (e.g. solid-state refrigeration, solar panels, thermoelectric devices).
