Exploring new route to boost thermoelectricity: phonon Drag enHacement through external phonon bath – DragHunt

The DragHunt project aims at opening new ways to improve the thermoelectric efficiency of materials, by exploring, both theoretically and experimentally, the phonon drag effect, which arises from the momentum transfer (or drag) between the out-of-equilibrium phonon and electron populations, and which is responsible for the strong increase in Seebeck and Peltier coefficients of thermoelectric materials at low temperature. The concept we aim to explore is the use of substrate as an external phonon bath to provide additional out-of-equilibrium phonons, in order to enhance phonon drag effect and shift it to higher temperatures in the conducting channel. To this end, we aim to develop a numerical approach which would allow to describe the coupled transport of charge and heat carriers at the interface between a conducting system and a phonon bath, with the specific focus on phonon drag effect. In parallel, phonon drag effect will be studied experimentally, on a model system consisting of graphitic conduction channels buried in a diamond matrix. The goal of this project is thus, by means of numerical simulation and by extensive experimental investigation of a chosen system, to identify the main factors (such as electronic band structure, phonon spectra in the two sub-systems, phonon transmission at the interface) which can enable phonon drag enhancement and shift it to higher temperatures. To achieve this goal, we propose to unite our complementary expertise in spectroscopic and thermoelectric measurements (ILM), in ab initio description of phonon drag effect (LSI) and in description of charge (C2N) and thermal (SATIE) transport including interfaces in order to explore, on the basis of preliminary results obtained by our respective teams, the possibility of enhancing phonon drag by tailoring systems made of a conductor and an external phonon bath.