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Enhanced Thermopower in a Magnetic Semiconductor EuTe4 with Multiple Charge-Density-Wave Instabilities

Hidefumi Takahashi1,2,*, Kiichiro Yoshida1, Akitoshi Nakano3, and Shintaro Ishiwata1,2,†

  • 1Division of Materials Physics and Center for Spintronics Research Network, Graduate School of Engineering Science, The University of Osaka, Osaka 560-8531, Japan
  • 2Spintronics Research Network Division, Institute for Open and Transdisciplinary Research Initiatives, The University of Osaka, Yamadaoka 2-1, Suita, Osaka, 565-0871, Japan
  • 3Department of Physics, Nagoya University, Nagoya 464-8602, Japan

  • *Contact author: takahashi.hidefumi.es@osaka-u.ac.jp
  • †Contact author: ishiwata.shintaro.es@osaka-u.ac.jp
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PRX Energy 4, 033009 – Published 21 August, 2025

DOI: https://doi.org/10.1103/9bvh-3r6w

Abstract

We investigate the layered magnetic semiconductor EuTe4, focusing on its intricate charge-density-wave (CDW) states near and above room temperature through single-crystal x-ray diffraction (XRD), magnetic, and thermoelectric measurements. The XRD measurement revealed that the CDW state inducing the polar lattice distortion persists even at 650 K, demonstrating its remarkable thermal stability. Notably, the Seebeck coefficient near room temperature reaches values exceeding 500 µV K−1. This large Seebeck coefficient, not fully captured by a simple band calculation, is comparable to those observed in heavy-electron semiconducting oxides, suggesting the importance of electron correlation and spin- and lattice instabilities. Furthermore, potentially reflecting the competition of two types of CDW state, the thermal conductivity near room temperature is as low as 0.02 W cm−1 K−1. As a result, the thermoelectric figure of merit zT reaches 0.22 at 460 K. These findings establish EuTe4 as a compelling platform to explore novel types of thermoelectric materials with multiple electronic instability.

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Popular Summary

In this work, the authors synthesized single crystals of the layered magnetic semiconductor EuTe4 and scrutinized its charge density wave (CDW) state, magnetism, and thermoelectric behavior. Remarkably, the CDW of EuTe4 persists up to ∼650 K, which is far beyond the stability range of typical CDW materials and indicates robust electron-lattice coupling. Near room temperature the Seebeck coefficient exceeds 500 μV/K, while low resistivity and thermal conductivity yield a figure of merit zT ≈ 0.1, competitive with some commercial thermoelectric materials. The huge Seebeck coefficient cannot be reproduced by simple band calculations. This implies that complex effects including electron correlations, multiple CDWs, and lattice fluctuations play a key role. EuTe4 therefore offers a rare platform where ultra stable CDWs, magnetism, and high thermoelectric performance coexist. This unique materials system may enable novel strategies such as carrier doping or pressure tuning to create efficient waste heat harvesters and solid state cooling devices.

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References (62)

  1. G. Grüner, The dynamics of charge-density waves, Rev. Mod. Phys. 60, 1129 (1988).
  2. K. Nakanishi, H. Takatera, Y. Yamada, and H. Shiba, The nearly commensurate phase and effect of harmonics on the successive phase transition in 1T-TaS2, J. Phys. Soc. Jpn. 43, 1509 (1977).
  3. S. Tanda, T. Sambongi, T. Tani, and S. Tanaka, X-ray study of charge density wave structure in 1T-TaS2, J. Phys. Soc. Jpn 53, 476 (1984).
  4. R. E. Thomson, B. Burk, A. Zettl, and J. Clarke, Scanning tunneling microscopy of the charge-density-wave structure in 1T-TaS2, Phys. Rev. B 49, 16899 (1994).
  5. G. Grüner, A. Zawadowski, and P. M. Chaikin, Nonlinear conductivity and noise due to charge-density-wave depinning in NbSe3, Phys. Rev. Lett. 46, 511 (1981).
  6. G. Liu, B. Debnath, T. R. Pope, T. T. Salguero, R. K. Lake, and A. A. Balandin, A charge-density-wave oscillator based on an integrated tantalum disulfide-boron nitride-graphene device operating at room temperature, Nat. Nanotechnol. 11, 845 (2016).
  7. A. A. Balandin, S. V. Zaitsev-Zotov, and G. Grüner, Charge-density-wave quantum materials and devices—New developments and future prospects, Appl. Phys. Lett. 119, 170401 (2021).
  8. G. Liu, E. X. Zhang, C. D. Liang, M. A. Bloodgood, T. T. Salguero, D. M. Fleetwood, and A. A. Balandin, Total-ionizing-dose effects on threshold switching in 1T-TaS2 charge density wave devices, IEEE Electron Device Lett. 38, 1724 (2017).
  9. A. Khitun, G. Liu, and A. A. Balandin, Two-dimensional oscillatory neural network based on room-temperature charge-density-wave devices, IEEE Trans. Nanotechnol. 16, 860 (2017).
  10. A. G. Khitun, A. K. Geremew, and A. A. Balandin, Transistor-less logic circuits implemented with 2-D charge density wave devices, IEEE Electron Device Lett. 39, 1449 (2018).
  11. E. DiMasi, M. C. Aronson, J. F. Mansfield, B. Foran, and S. Lee, Chemical pressure and charge-density waves in rare-earth tritellurides, Phys. Rev. B 52, 14516 (1995).
  12. G.-H. Gweon, J. D. Denlinger, J. A. Clack, J. W. Allen, C. G. Olson, E. DiMasi, M. C. Aronson, B. Foran, and S. Lee, Direct observation of complete Fermi surface, imperfect nesting, and gap anisotropy in the high-temperature incommensurate charge-density-wave Compound SmTe3, Phys. Rev. Lett. 81, 886 (1998).
  13. V. Brouet, W. L. Yang, X. J. Zhou, Z. Hussain, N. Ru, K. Y. Shin, I. R. Fisher, and Z. X. Shen, Fermi surface reconstruction in the CDW state of CeTe3 observed by photoemission, Phys. Rev. Lett. 93, 126405 (2004).
  14. K. Yumigeta, Y. Qin, H. Li, M. Blei, Y. Attarde, C. Kopas, and S. Tongay, Advances in rare-earth tritelluride quantum materials: Structure, properties, and synthesis, Adv. Sci. (Weinh.) 8, e2004762 (2021).
  15. N. Ru, J.-H. Chu, and I. R. Fisher, Magnetic properties of the charge density wave compounds RTe3 (R = Y,La,Ce,Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,andTm), Phys. Rev. B 78, 012410 (2008).
  16. J. J. Hamlin, D. A. Zocco, T. A. Sayles, M. B. Maple, J.-H. Chu, and I. R. Fisher, Pressure-induced superconducting phase in the charge-density-wave compound terbium tritelluride, Phys. Rev. Lett. 102, 177002 (2009).
  17. D. A. Zocco, J. J. Hamlin, K. Grube, J.-H. Chu, H.-H. Kuo, I. R. Fisher, and M. B. Maple, Pressure dependence of the charge-density-wave and superconducting states in GdTe3, TbTe3, and DyTe3, Phys. Rev. B 91, 205114 (2015).
  18. S. Akatsuka, S. Esser, S. Okumura, R. Yamabe, R. Yamada, M. M. Hirschmann, S. Aji, J. S. White, S. Gao, Y. Onuki, T.-H. Arima, T. Nakajima, and M. Hirschberger, Non-coplanar helimagnetism in the layered van-der-Waals metal DyTe3, Nat. Commun. 15, 4291 (2024).
  19. D. Wu, Q. M. Liu, S. L. Chen, G. Y. Zhong, J. Su, L. Y. Shi, L. Tong, G. Xu, P. Gao, and N. L. Wang, Layered semiconductor EuTe4 with charge density wave order in square tellurium sheets, Phys. Rev. Mater. 3, 024002 (2019).
  20. Q. Q. Zhang, et al., Thermal hysteretic behavior and negative magnetoresistance in the charge density wave material EuTe4, Phys. Rev. B 107, 115141 (2023).
  21. C. Zhang, et al., Angle-resolved photoemission spectroscopy study of charge density wave order in the layered semiconductor EuTe4, Phys. Rev. B 106, L201108 (2022).
  22. B. Q. Lv, A. Zong, D. Wu, Z. Nie, Y. Su, D. Choi, B. Ilyas, B. T. Fichera, J. Li, E. Baldini, M. Mogi, Y.-B. Huang, H. C. Po, S. Meng, Y. Wang, N. L. Wang, and N. Gedik, Coexistence of interacting charge density waves in a layered semiconductor, Phys. Rev. Lett. 132, 206401 (2024).
  23. B. Q. Lv, et al., Unconventional hysteretic transition in a charge density wave, Phys. Rev. Lett. 128, 036401 (2022).
  24. R. Rathore, A. Pathak, M. K. Gupta, R. Mittal, R. Kulkarni, A. Thamizhavel, H. Singhal, A. H. Said, and D. Bansal, Evolution of static charge density wave order, amplitude mode dynamics, and suppression of Kohn anomalies at the hysteretic transition in EuTe4, Phys. Rev. B 107, 024101 (2023).
  25. K. Xiao, W.-H. Dong, X. Wang, J. Yu, D. Fu, Z. Hu, Y. Guo, Q. Zhang, X. Hou, Y. Guo, L. Yang, Y. Xu, P. Tang, W. Duan, Q. Xue, and W. Li, Hidden charge order and multiple electronic instabilities in EuTe4, Nano Lett. 24, 7681 (2024).
  26. B. Q. Lv, Y. Su, A. Zong, Q. Liu, D. Wu, N. F. Q. Yuan, Z. Nie, J. Li, S. Sarker, S. Meng, J. P. C. Ruff, N. L. Wang, and N. Gedik, Large moiré superstructure of stacked incommensurate charge density waves, http://arxiv.org/abs/2501.09715.
  27. Q. Liu, et al., Room-temperature non-volatile optical manipulation of polar order in a charge density wave, Nat. Commun. 15, 8937 (2024).
  28. R. Venturini, M. Rupnik, J. Gašperlin, J. Lipič, P. Šutar, Y. Vaskivskyi, F. Ščepanović, D. Grabnar, D. Golež, and D. Mihailovic, Electrically driven non-volatile resistance switching between charge density wave states at room temperature, http://arxiv.org/abs/2412.13094.
  29. H. Takahashi, K. Aono, Y. Nambu, R. Kiyanagi, T. Nomoto, M. Sakano, K. Ishizaka, R. Arita, and S. Ishiwata, Competing spin modulations in the magnetically frustrated semimetal EuCuSb, Phys. Rev. B 102, 174425 (2020).
  30. H. Takahashi, K. Akiba, M. Takahashi, A. H. Mayo, M. Ochi, T. C. Kobayashi, and S. Ishiwata, Superconductivity in a magnetic Rashba semimetal EuAuBi, J. Phys. Soc. Jpn. 92, 013701 (2023).
  31. See the Supplemental Material at http://link.aps.org/supplemental/10.1103/9bvh-3r6w for the scanning electron microscopy, EDX, X-ray diffraction, TG-DTA, magnetoresistance, and Hall resistivity results, the analysis for the magnetic susceptibility, the estimation of the power factor, and the details of the band calculations. References [[19, 20, 21, 22, 23, 32, 33, 34, 35, 36, 37]] are cited in Supplemental Material.
  32. A. Pathak, M. K. Gupta, R. Mittal, and D. Bansal, Orbital- and atom-dependent linear dispersion across the Fermi level induces charge density wave instability in EuTe4, Phys. Rev. B 105, 035120 (2022).
  33. H. Ghamri, Y. Djaballah, and A. Belgacem-Bouzida, Thermodynamic modeling of the Eu–Te and Te–Yb systems, J. Alloys Compd. 643, 121 (2015).
  34. H. Sakai, K. Ikeura, M. S. Bahramy, N. Ogawa, D. Hashizume, J. Fujioka, Y. Tokura, and S. Ishiwata, Critical enhancement of thermopower in a chemically tuned polar semimetal MoTe2, Sci. Adv. 2, e1601378 (2016).
  35. H. Takahashi, T. Akiba, K. Imura, T. Shiino, K. Deguchi, N. K. Sato, H. Sakai, M. S. Bahramy, and S. Ishiwata, Anticorrelation between polar lattice instability and superconductivity in the Weyl semimetal candidate MoTe2, Phys. Rev. B 95, 100501 (2017).
  36. H. Takahashi, K. Hasegawa, T. Akiba, H. Sakai, M. S. Bahramy, and S. Ishiwata, Giant enhancement of cryogenic thermopower by polar structural instability in the pressurized semimetal MoTe2, Phys. Rev. B 100, 195130 (2019).
  37. A. Nakano, A. Yamakage, U. Maruoka, H. Taniguchi, Y. Yasui, and I. Terasaki, Giant Peltier conductivity in an uncompensated semimetal Ta2PdSe6, J. Phys. Energy 3, 044004 (2021).
  38. P. Giannozzi, et al., QUANTUM ESPRESSO: A modular and open-source software project for quantum simulations of materials, J. Phys. Condens. Matter 21, 395502 (2009).
  39. P. Giannozzi, et al., Advanced capabilities for materials modelling with Quantum ESPRESSO, J. Phys. Condens. Matter 29, 465901 (2017).
  40. Quantum ESPRESSO, http://www.quantum-espresso.org
  41. A. Dal Corso, Pseudopotentials periodic table: From H to Pu, Comput. Mater. Sci. 95, 337 (2014).
  42. M. Kawamura, FermiSurfer: Fermi-surface viewer providing multiple representation schemes, Comput. Phys. Commun. 239, 197 (2019).
  43. G. K. H. Madsen and D. J. Singh, BoltzTraP. A code for calculating band-structure dependent quantities, Comput. Phys. Commun. 175, 67 (2006).
  44. J. Yin, C. Wu, L. Li, J. Yu, H. Sun, B. Shen, B. A. Frandsen, D.-X. Yao, and M. Wang, Large negative magnetoresistance in the antiferromagnetic rare-earth dichalcogenide EuTe2, Phys. Rev. Mater. 4, 013405 (2020).
  45. H. Takahashi, Y. Yasui, I. Terasaki, and M. Sato, Effects of ppm-level imperfection on the transport properties of FeSb2 single crystals, J. Phys. Soc. Jpn. 80, 054708 (2011).
  46. B. C. Sales, D. Mandrus, and R. K. Williams, Filled skutterudite antimonides: A new class of thermoelectric materials, Science 272, 1325 (1996).
  47. D.-L. Ma, P. Bag, Y.-K. Kuo, C.-N. Kuo, and C. S. Lue, Thermoelectric and specific heat characteristics of the charge density wave compounds RTe3 (R = Gd,Tb,Dy,Ho,andEr), Phys. Rev. B 111, 165420 (2025).
  48. H. Imai, Y. Shimakawa, and Y. Kubo, Large thermoelectric power factor in TiS2 crystal with nearly stoichiometric composition, Phys. Rev. B 64, 241104(R) (2001).
  49. T. Caillat, A. Borshchevsky, and J.-P. Fleurial, Properties of single crystalline semiconducting CoSb3, J. Appl. Phys. 80, 4442 (1996).
  50. T. H. Geballe and G. W. Hull, Seebeck effect in germanium, Phys. Rev. 94, 1134 (1954).
  51. L. Huang, T. Liu, A. Huang, G. Yuan, J. Wang, J. Liao, X. Lei, Q. Zhang, and Z. Ren, Enhanced thermoelectric performance of nominal 19-electron half-Heusler compound NbCoSb with intrinsic Nb and Sb vacancies, Mater. Today Phys. 20, 100450 (2021).
  52. M. Mitra, A. Benton, M. S. Akhanda, J. Qi, M. Zebarjadi, D. J. Singh, and S. J. Poon, Conventional half-Heusler alloys advance state-of-the-art thermoelectric properties, Mater. Today Phys. 28, 100900 (2022).
  53. Y. Ren, Q. Jiang, J. Yang, Y. Luo, D. Zhang, Y. Cheng, and Z. Zhou, Enhanced thermoelectric performance of MnTe via Cu doping with optimized carrier concentration, J. Mater. 2, 172 (2016).
  54. Y. Zheng, T. Lu, Md M. H. Polash, M. Rasoulianboroujeni, N. Liu, M. E. Manley, Y. Deng, P. J. Sun, X. L. Chen, R. P. Hermann, D. Vashaee, J. P. Heremans, and H. Zhao, Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe, Sci. Adv. 5, eaat9461 (2019).
  55. C. Collignon, P. Bourges, B. Fauqué, and K. Behnia, Heavy nondegenerate electrons in doped strontium titanate, Phys. Rev. X 10, 031025 (2020).
  56. V. Zlatić, R. Monnier, J. K. Freericks, and K. W. Becker, Relationship between the thermopower and entropy of strongly correlated electron systems, Phys. Rev. B 76, 085122 (2007).
  57. J. Mravlje and A. Georges, Thermopower and entropy: Lessons from Sr2RuO4, Phys. Rev. Lett. 117, 036401 (2016).
  58. H. Takahashi, S. Ishiwata, R. Okazaki, Y. Yasui, and I. Terasaki, Enhanced thermopower via spin-state modification, Phys. Rev. B 98, 024405 (2018).
  59. T. D. Yamamoto, H. Taniguchi, Y. Yasui, S. Iguchi, T. Sasaki, and I. Terasaki, Magneto-thermopower in the weak ferromagnetic oxide CaRu0.8Sc0.2O3: An experimental test for the Kelvin formula in a magnetic material, J. Phys. Soc. Jpn. 86, 104707 (2017).
  60. R. Rathore, H. Singhal, V. Dwij, M. K. Gupta, A. Pathak, J. A. Chakera, R. Mittal, A. P. Roy, A. Babu, R. Kulkarni, A. Thamizhavel, A. H. Said, and D. Bansal, Nonlocal probing of amplitude mode dynamics in charge-density-wave phase of EuTe4, Ultrafast Sci. 3, 0041 (2023).
  61. H. Fukuyama and M. Ogata, Theory of phason drag effect on thermoelectricity, Phys. Rev. B 102, 205136 (2020).
  62. https://doi.org/10.5281/zenodo.16758071.

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PRX Energy 4, 033009– Published 21 August, 2025
  • Received 17 April 2025
  • Revised 22 July 2025
  • Accepted 29 July 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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