Abstract
We report the electronic structure of the thermoelectric semimetal Ta2PdSe6 with a large thermoelectric power factor and giant Peltier conductivity by means of angle-resolved photoemission spectroscopy (ARPES). The ARPES spectra reveal the coexistence of a sharp hole band with a light electron mass and a broad electron band with a relatively heavy electron mass, which originate from different quasi-one-dimensional (Q1D) chains in Ta2PdSe6. Moreover, the electron band around the Brillouin-zone (BZ) boundary shows a replica structure with respect to the energy originating from plasmonic polarons due to electron-plasmon interactions. The different scattering effects and interactions in each atomic chain lead to asymmetric transport lifetimes of carriers: a large Seebeck coefficient can be realized even in a semimetal. Our findings pave the way for exploring the thermoelectric materials in previously overlooked semimetals and provide a new platform for low-temperature thermoelectric physics, which has been challenging with semiconductors.
Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request.
References
Shekhar, C. Extremely large magnetoresistance and ultrahigh mobility in the topological Weyl semimetal candidate NbP. Nat. Phys. 11, 645 (2015).
Liang, T. et al. Ultrahigh mobility and giant magnetoresistance in the Dirac semimetal Cd3As2. Nat. Mater. 14, 280 (2015).
Mott, N. F. and Jones, H. The Theory of the Properties of Metals and Alloys (Oxford University Press, Oxford, U.K., 1936).
Cutler, M. & Mott, N. F. Observation of Anderson localization in an electron gas. Phys. Rev. 181, 1336 (1969).
Markov, M. et al. Thermoelectric properties of semimetals. Sci. Rep. 8, 9876 (2018).
Markov, M., Rezaei, S. E., Sadeghi, S. N., Esfarjani, K. & Zebarjadi, M. Thermoelectric properties of semimetals. Phys. Rev. Mater. 3, 095401 (2019).
Shimizu, S. et al. Giant thermoelectric power factor in ultrathin FeSe superconductor. Nat. Commun. 10, 825 (2019).
Matsubara, M., Yamamoto, T. & Fukuyama, H. Two-band model with high thermoelectric power factor and its application to FeSe thin film. J. Phys. Soc. Jpn. 92, 104704 (2023).
Nakano, A., Maruoka, U., Kato, F., Taniguchi, H. & Terasaki, I. Room temperature thermoelectric properties of isostructural selenides Ta2PdS6 and Ta2PdSe6. J. Phys. Soc. Jpn. 90, 033702 (2021).
Nakano, A. et al. Correlation between thermopower and carrier mobility in the thermoelectric semimetal Ta2PdSe6. J. Phys.: Energy 3, 044004 (2021).
Nakano, A., Maruoka, U. & Terasaki, I. Correlation between thermopower and carrier mobility in the thermoelectric semimetal Ta2PdSe6. Appl. Phys. Lett. 121, 153903 (2022).
Blaha, P., Schwarz, K., Madsen, G. K. H., Kvasnicka, D. & Luitz, J. WIEN2k: An Augmented Plane Wave plus Local Orbitals Program for Calculating Crystal Properties (Technische Universität Wien, Austria, 2002).
Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865 (1996).
Becke, A. D. & Johnson, E. R. A simple effective potential for exchange. J. Chem. Phys. 124, 221101 (2006).
Tran, F. & Blaha, P. Accurate band gaps of semiconductors and insulators with a semilocal exchange-correlation potential. Phys. Rev. Lett. 102, 226401 (2009).
Gonze, X. et al. The Abinit project: impact, environment and recent developments. Comput. Phys. Commun. 248, 107042 (2020).
Romero, A. H. et al. ABINIT: overview and focus on selected capabilities. J. Chem. Phys. 152, 124102 (2020).
Blöchl, P. E. Projector augmented-wave method. Phys. Rev. Lett. 50, 17953 (1994).
Torrent, M., Jollet, F., Bottin, F., Zérah, G. & Gonze, X. Implementation of the projector augmented-wave method in the ABINIT code: application to the study of iron under pressure. Comput. Mater. Sci. 42, 337 (2008).
Gonze, X. & Lee, C. Dynamical matrices, Born effective charges, dielectric permittivity tensors, and interatomic force constants from density-functional perturbation theory. Phys. Rev. B 55, 10355 (1997).
Fuchs, M. & Scheffler, M. Ab initio pseudopotentials for electronic structure calculations of poly-atomic systems using density-functional theory. Comput. Phys. Commun. 119, 67 (1999).
Yang, H. et al. Pressure-induced superconductivity in quasi-one-dimensional semimetal Ta2PdSe6. Phys. Rev. Mater. 6, 084803 (2022).
Nakano, A. et al. Scattering Engineering for High Power Factor Semimetals Proved by Shubnikov-de Haas Oscillation and Anisotropic Resistivity. Adv. Electron. Mater 11, e00279 (2025).
Wang, Y. et al. Large magnetoresistance and nontrivial Fermi surface topology in quasi-one-dimensional Ta2PdSe6. Appl. Phys. Lett. 124, 203101 (2024).
Yang, L. et al. Quasi-one-dimensional Ta2PdSe6 with strong topological surface states for high-performance and polarization-sensitive terahertz detection. Nano Lett. 25, 7690–7698 (2025).
Kato, F. et al. Enhanced cryogenic thermoelectricity in semimetal Ta2PdSe6 through non-Fermi liquid-like charge and heat transport. Adv. Phys. Res. 3, 2400063 (2024).
Nakano, A. & Terasaki, I. Large Nernst effect in the high-mobility semimetal Ta2PdSe6. J. Phys. Soc. Jpn. 93, 103703 (2024).
Chen, C., Avila, J. osé, Frantzeskakis, E., Levy, A. & Asensio, M. C. Observation of a two-dimensional liquid of Fröhlich polarons at the bare SrTiO3 surface. Nat. Commun. 6, 8585 (2015).
Wang, Z. et al. Tailoring the nature and strength of electron-phonon interactions in the SrTiO3(001) 2D electron liquid. Nat. Mater. 15, 835–839 (2016).
Faeth, B. D. et al. Interfacial electron-phonon coupling constants extracted from intrinsic replica bands in monolayer FeSe/SrTiO3. Phys. Rev. Lett. 127, 016803 (2021).
Li, F. & Sawatzky, G. A. Electron phonon coupling versus photoelectron energy loss at the origin of replica bands in photoemission of FeSe on SrTiO3. Phys. Rev. Lett. 120, 237001 (2018).
Moser, S. et al. Tunable polaronic conduction in anatase TiO. Phys. Rev. Lett. 110, 196403 (2013).
Yukawa, R. et al. Phonon-dressed two-dimensional carriers on the ZnO surface. Phys. Rev. B 94, 165313 (2016).
Cancellieri, C. et al. Polaronic metal state at the LaAlO3/SrTiO3 interface. Nat. Commun. 7, 10386 (2016).
Lee, J. J. et al. Interfacial mode coupling as the origin of the enhancement of TC in FeSe films on SrTiO3. Nature 515, 245–248 (2014).
Zhang, C. et al. Ubiquitous strong electron-phonon coupling at the interface of FeSe/SrTiO3. Nat. Commun. 8, 14468 (2017).
Liu, C. et al. High-order replica bands in monolayer FeSe/SrTiO3 revealed by polarization-dependent photoemission spectroscopy. Nat. Commun. 12, 4573 (2021).
Caruso, F., Lambert, H. & Giustino, F. Band structures of plasmonic polarons. Phys. Rev. Lett. 114, 146404 (2015).
Caruso, F., Verdi, C., Poncé, S. & Giustino, F. Electron-plasmon and electron-phonon satellites in the angle-resolved photoelectron spectra of n-doped anatase TiO2. Phys. Rev. B 97, 165113 (2018).
Riley, J. M. et al. Crossover from lattice to plasmonic polarons of a spin-polarised electron gas in ferromagnetic EuO. Nat. Commun. 9, 2305 (2018).
Caruso, F. et al. Two-dimensional plasmonic polarons in n-doped monolayer MoS2. Phys. Rev. B 103, 205152 (2021).
ren Ulstrup, S. ø et al. Observation of interlayer plasmon polaron in graphene/WS2 heterostructures. Nat. Commun. 15, 3845 (2024).
Nakano, A. et al. Exciton transport in the electron-hole system Ta2NiSe5. J. Phys. Soc. Jpn. 88, 113706 (2019).
Ohta, H. et al. Giant thermoelectric Seebeck coefficient of a two-dimensional electron gas in SrTiO3. Nat. Mater. 6, 129–134 (2007).
Choi, W. S., Ohta, H., Moon, S. J., Lee, Y. S. & Noh, T. W. Dimensional crossover of polaron dynamics in Nb:SrTiO3/SrTiO3 superlattices: possible mechanism of thermopower enhancement. Phys. Rev. B 82, 024301 (2010).
Choi, W. S., Yoo, H. K. & Ohta, H. Polaron transport and thermoelectric behavior in La-Doped SrTiO3 thin films with elemental vacancies. Adv. Funct. Mater. 25, 799–804 (2015).
Zhao, L.-D. et al. Ultrahigh power factor and thermoelectric performance in hole-doped single-crystal SnSe. Science 351, 141–144 (2016).
de Cotret, L. P. R. et al. Direct visualization of polaron formation in the thermoelectric SnSe. Proc. Natl. Acad. Sci. USA 116, 450 (2019).
Guster, B., Vasilchenko, V., Azizi, M., Giantomassi, M. & Gonze, X. Large cylindrical polaron in orthorhombic SnSe: a theoretical study. Phys. Rev. Mater. 7, 064604 (2023).
Snyder, G. J., Caillat, T. & Fleurial, J.-P. Thermoelectric, transport, and magnetic properties of the polaron semiconductor FexCr3−xSe4. Phys. Rev. B 62, 10185 (2000).
Mannella, N. et al. Nodal quasiparticle in pseudogapped colossal magnetoresistive manganites. Nature 438, 474–478 (2005).
Mannella, N. et al. Polaron coherence condensation as the mechanism for colossal magnetoresistance in layered manganites. Phys. Rev. B 76, 233102 (2007).
Kitamura, M. et al. Development of a versatile micro-focused angle-resolved photoemission spectroscopy system with Kirkpatrick-Baez mirror optics. Rev. Sci. Instrum. 93, 033906 (2022).
Homma, K. & Izumi, F. VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr. 44, 1272 (2011).
Acknowledgements
The authors would like to thank H. Fukuyama and M. Matsubara for fruitful discussions, T. Ishida for experimental support, and A. Honma, S. Souma, K. Ozawa, and T. Sato for technical assistance with BL-28A at Photon Factory. The synchrotron radiation experiment was performed with the approval of Photon Factory (Proposal Nos. 2018S2-001, 2019G122, 2021G101, 2021S2-001, 2022G077, and 2024G081) and HSRC (Proposal Nos. 21AG030, 21BG022, 22BG010, and 25BG029). This work was supported by Japan Society for the Promotion of Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI Nos. 17H06136, 21K13878, 21K13882, 23K13059, 24H01621, 25K07184, and 25K07226).
Author information
Authors and Affiliations
Contributions
D.O., A.N., and I.T. designed the research. D.O. performed the ARPES measurements with support from M.A., M.K., K.H., and T.Y.'s research. A.N., U.M., and I.T. contributed samples. T.H. calculated the phonon density of states. D.O. analyzed the data and wrote the paper. All authors reviewed the manuscript.
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Ootsuki, D., Nakano, A., Maruoka, U. et al. Band-selective plasmonic polaron in thermoelectric semimetal Ta2PdSe6 with ultra-high power factor. npj Quantum Mater. (2026). https://doi.org/10.1038/s41535-026-00858-8
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41535-026-00858-8
