The 11th Special CMSM-ERATO Joint Seminar
(The 291st Special CMSM seminar)


Development of a Huge Power Factor by Controlling Electron Scattering

Prof. Akitoshi Nakano
Dept. of Physics, Nagoya Univ., Nagoya 464-8602, Japan
Date & Time: 15:00 - 16:00, Nov. 20th (Thu), 2025.
Place: 8F Conference Room, Main Bldg., Sengen.

Abstract:

Thermoelectric research has traditionally focused on semiconductors, where optimizing carrier concentration within the degenerate regime has been the key to achieving high performance[1]. In contrast, semimetals—having overlapping electron and hole bands—have long been excluded from thermoelectric design because bipolar diffusion tends to cancel the Seebeck voltage[2]. Here, we propose a new design strategy that leverages carrier scattering asymmetry in semimetals to achieve a large power factor. Using the quasi-one-dimensional transition-metal chalcogenide Ta2PdSe6, we demonstrate an exceptionally high power factor of 2.4 mW cm-1 K-2[3], exceeding that of conventional thermoelectric semiconductors such as Bi2Te3 by two orders of magnitude. Transport and two-carrier model analyses reveal that electron and hole scattering times differ by nearly two orders, resulting in dominant hole conduction with high mobility and a large Seebeck coefficient. This “uncompensated” semimetal state yields both high conductivity and thermopower, leading to the observed colossal power factor. The origin of this asymmetry is likely linked to density-wave fluctuations inherent in the quasi-one-dimensional electronic structure. These findings open a new route to thermoelectric materials design—scattering engineering—that exploits intrinsic asymmetries in semimetals without relying on chemical doping.

References
[1] J. Snyder, et al., Nature Materials 7, 105-114 (2008)
[2] M. Markov, et al., Phys. Rev. M 3, 095401 (2019)
[3] A. Nakano, et al., J. Phys. Energy 3, 044004 (2021)

(Contact)

Ken-ichi Uchida, Spin Caloritronics Group　
E-mail: UCHIDA.Kenichi[at]nims.go.jp