Boosting Thermoelectric Efficiency through Electron-Phonon Interactions and Low-Dimensional Fermi Surfaces

Cheng-Lung Chen^1*, Te-Hsien Wang¹, Hung-Han Chou¹, Kai-Nien Yang¹, Yi-Xuan He¹, Yun-Hsuan Hsieh¹

¹Department of Physics and Institute of Nanoscience, National Chung Hsing University, Taichung, Taiwan

* Presenter:Cheng-Lung Chen, email:chencl@dragon.nchu.edu.tw

In this study, we uncover the underlying physics responsible for the high thermoelectric performance of Sb-Bi codoped GeTe crystals (Ge₀.₈₆Sb₀.₀₈Bi₀.₀₆)Te, which exhibit an extraordinary thermoelectric figure of merit (zT ≈ 2.7) at 700 K. Our inelastic neutron scattering (INS) measurements revealed a Kohn anomaly, a key indicator of strong electron-phonon (EP) interactions within the material. Density functional theory (DFT) analysis links these robust EP interactions to Fermi surface nesting in the low-dimensional Fermi surface, which is characterized by high valley degeneracy. This electronic configuration is a crucial factor in achieving the material’s exceptionally low lattice thermal conductivity and high zT. Our findings point to the potential for achieving ultrahigh zT values not only in GeTe-based alloys but also in other IV-VI semiconductors, such as PbTe, SnTe, and SnSe, that exhibit similar electronic features. By exploring the complex nature of EP interactions and their dependence on Fermi surface topology, this research advances the fundamental understanding of the physics governing thermoelectric efficiency. The insights gained here could pave the way for future innovations in the design of advanced thermoelectric materials, driving progress in energy conversion technologies.

Keywords: Fermi Surface Nesting, Kohn anomaly, Thermoelectrics, Sustainable Energy, Thermal conductivity