Valley-selective electron-phonon scattering in thermoelectric semimetal Ta₂PdSe₆

High-performance thermoelectric materials have long been looked for mainly in slightly doped insulators or semiconductors, but electron-hole asymmetry in relaxation time can result in a high thermoeletric power factor even in metallic systems. Quasi-one-dimensional transition-metal chalcogenide Ta₂PdSe₆ is a promising thermoelectric semimetal exhibiting high thermoelectric performance at low temperatures [1,2]. It was experimentally found that the mobilities of electron and hole carriers differ by an order of magnitude at low temperature. For theoretical studies of this compound, while the electronic band structure and the phonon band structure have been investigated in some studies, the scattering properties of the carriers have not been investigated.

In this study, we perform first-principles calculation of electron-phonon scattering in Ta₂PdSe₆ using Quantum ESPRESSO and EPW. We find that the electron self-energy is strongly k-dependent and strong intervalley scattering takes place between the electron pocket and the highest valence band at the Gamma point. Our study clarifies intriguing valley-selective electron-phonon scattering in Ta₂PdSe₆.

[1] A. Nakano et al., J. Phys. Energy 3, 044004 (2021). [2] A. Nakano et al., J. Phys. Soc. Jpn. 90, 033702 (2021).