Electron-hole dichotomy and enhancement of thermoelectric power factor by electron-hole-asymmetric relaxation time: a model study on a two-valley system with strong intervalley scattering

The role of electron-phonon scattering in thermoelectric transport has been paid much attention, especially in multivalley systems. In this study [1], we analyze a minimal model for a two-electron-valley system with intravalley and intervalley electron-phonon scattering; accordingly, find three electron transport regimes under strong intervalley scattering. In addition to the usual power factor (PF) peak near the band edge, strong electron-hole asymmetry of electron relaxation time due to the intervalley scattering enhances the Seebeck coefficient and thus PF for larger doping concentration. For example, when electron carriers are strongly affected by the intervalley scattering while hole carriers are not, strongly electron-hole-asymmetric relaxation time results in a large Seebeck coefficient. This situation can also cause an anomalous sign change of the Seebeck coefficient as pointed out in Ref. [2]. Our finding sheds light on unexplored thermoelectric transport under the strong electron-phonon scattering.



[1] M. Ochi, arXiv:2306.04075 (2023). [2] N. S. Fedorova, A. Cepellotti, and B. Kozinsky, Adv. Funct. Mater. 32, 2111354 (2022).