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Interaction-driven giant thermopower in magic-angle twisted bilayer graphene

Nature Physics volume 18, pages 691–698 (2022)Cite this article

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Abstract

Magic-angle twisted bilayer graphene has proved to be a fascinating platform to realize and study emergent quantum phases arising from the strong correlations in its flat bands. Thermal transport phenomena, such as thermopower, are sensitive to the particle–hole asymmetry, making them a crucial tool to probe the underlying electronic structure of this material. Here we have carried out thermopower measurements of magic-angle twisted bilayer graphene as a function of carrier density, temperature and magnetic field. We report the observation of an unusually large thermopower reaching a value of the order of 100 μV K−1 at a low temperature of 1 K. The thermopower exhibits peak-like features that violate the Mott formula in close correspondence to the resistance peaks appearing around the integer filling of the moiré bands, including the Dirac point. We show that the large thermopower peaks and their associated behaviour arise from the emergent highly particle–hole-asymmetric electronic structure, due to the sequential filling of the moiré flat bands and the associated recovery of Dirac-like physics. Furthermore, the thermopower shows an anomalous peak around the superconducting transition, which points towards the possible role of superconducting fluctuations in magic-angle twisted bilayer graphene.

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Fig. 1: Thermopower for different band structures.
Fig. 2: Thermopower measurement set-up and device response.
Fig. 3: Thermopower response at integer moiré fillings.
Fig. 4: Thermopower across the superconducting transition.
Fig. 5: Cascade of Dirac revivals and thermopower peaks around integer fillings.

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Source data are provided with this paper. Additional information related to this work is available from the corresponding author upon reasonable request.

References

  1. Bistritzer, R., & MacDonald, A. H. Moiré bands in twisted double-layer graphene. Proc. Natl Acad. Sci. USA 108, 12233–12237 (2011).

    Article  ADS  Google Scholar 

  2. Cao, Y. et al. Correlated insulator behaviour at half-filling in magic-angle graphene superlattices. Nature 556, 80–84 (2018).

    Article  ADS  Google Scholar 

  3. Cao, Y. et al. Unconventional superconductivity in magic-angle graphene superlattices. Nature 556, 43–50 (2018).

    Article  ADS  Google Scholar 

  4. Yankowitz, M. et al. Tuning superconductivity in twisted bilayer graphene. Science 363, 1059–1064 (2019).

    Article  ADS  Google Scholar 

  5. Wu, S., Zhang, Z., Watanabe, K., Taniguchi, T. & Andrei, E. Y. Chern insulators, van Hove singularities and topological flat bands in magic-angle twisted bilayer graphene. Nat. Mater. 20, 488–494 (2021).

    Article  ADS  Google Scholar 

  6. Saito, Y., Ge, J., Watanabe, K., Taniguchi, T. & Young, A. F. Independent superconductors and correlated insulators in twisted bilayer graphene. Nat. Phys. 16, 926–930 (2020).

    Article  Google Scholar 

  7. Lu, X. et al. Superconductors, orbital magnets and correlated states in magic-angle bilayer graphene. Nature 574, 653–657 (2019).

    Article  ADS  Google Scholar 

  8. Arora, H. S. et al. Superconductivity in metallic twisted bilayer graphene stabilized by WSe2. Nature 583, 379–384 (2020).

    Article  ADS  Google Scholar 

  9. Park, J. M., Cao, Y., Watanabe, K., Taniguchi, T. & Jarillo-Herrero, P. Tunable strongly coupled superconductivity in magic-angle twisted trilayer graphene. Nature 590, 249–255 (2021).

    Article  ADS  Google Scholar 

  10. Sharpe, A. L. et al. Emergent ferromagnetism near three-quarters filling in twisted bilayer graphene. Science 365, 605–608 (2019).

    Article  ADS  Google Scholar 

  11. Das, I. et al. Symmetry-broken Chern insulators and Rashba-like Landau-level crossings in magic-angle bilayer graphene. Nat. Phys. 17, 710–714 (2021).

    Article  Google Scholar 

  12. Nuckolls, K. P. et al. Strongly correlated Chern insulators in magic-angle twisted bilayer graphene. Nature 588, 610–615 (2020).

    Article  ADS  Google Scholar 

  13. Choi, Y. et al. Correlation-driven topological phases in magic-angle twisted bilayer graphene. Nature 589, 536–541 (2021).

    Article  ADS  Google Scholar 

  14. Stepanov, P. et al. Competing zero-field Chern insulators in superconducting twisted bilayer graphene. Phys. Rev. Lett. 127, 197701 (2021).

    Article  ADS  Google Scholar 

  15. Pierce, A. T. et al. Unconventional sequence of correlated Chern insulators in magic-angle twisted bilayer graphene. Nat. Phys. 17, 1210–1215 (2021).

    Article  Google Scholar 

  16. Serlin, M. et al. Intrinsic quantized anomalous Hall effect in a moiré heterostructure. Science 367, 900–903 (2020).

    Article  ADS  Google Scholar 

  17. Jiang, Y. et al. Charge order and broken rotational symmetry in magic-angle twisted bilayer graphene. Nature 573, 91–95 (2019).

    Article  ADS  Google Scholar 

  18. Cao, Y. et al. Nematicity and competing orders in superconducting magic-angle graphene. Science 372, 264–271 (2021).

    Article  ADS  Google Scholar 

  19. Rozen, A. et al. Entropic evidence for a Pomeranchuk effect in magic-angle graphene. Nature 592, 214–219 (2021).

    Article  ADS  Google Scholar 

  20. Saito, Y. et al. Isospin Pomeranchuk effect in twisted bilayer graphene. Nature 592, 220–224 (2021).

    Article  ADS  Google Scholar 

  21. Choi, Y. et al. Electronic correlations in twisted bilayer graphene near the magic angle. Nat. Phys. 15, 1174–1180 (2019).

    Article  Google Scholar 

  22. Xie, Y. et al. Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene. Nature 572, 101–105 (2019).

    Article  ADS  Google Scholar 

  23. Kerelsky, A. et al. Maximized electron interactions at the magic angle in twisted bilayer graphene. Nature 572, 95–100 (2019).

    Article  ADS  Google Scholar 

  24. Wong, D. et al. Cascade of electronic transitions in magic-angle twisted bilayer graphene. Nature 582, 198–202 (2020).

    Article  ADS  Google Scholar 

  25. Zondiner, U. et al. Cascade of phase transitions and Dirac revivals in magic-angle graphene. Nature 582, 203–208 (2020).

    Article  ADS  Google Scholar 

  26. Xu, Z. A., Ong, N. P., Wang, Y., Kakeshita, T. & Uchida, S. Vortex-like excitations and the onset of superconducting phase fluctuation in underdoped La2-xSrxCuO4. Nature 406, 486–488 (2000).

    Article  ADS  Google Scholar 

  27. Zuev, Y. M., Chang, W. & Kim, P. Thermoelectric and magnetothermoelectric transport measurements of graphene. Phys. Rev. Lett. 102, 096807 (2009).

    Article  ADS  Google Scholar 

  28. Checkelsky, J. G. & Ong, N. P. Thermopower and Nernst effect in graphene in a magnetic field. Phys. Rev. B 80, 081413 (2009).

    Article  ADS  Google Scholar 

  29. Nam, S.-G., Ki, D.-K. & Lee, H.-J. Thermoelectric transport of massive Dirac fermions in bilayer graphene. Phys. Rev. B 82, 245416 (2010).

    Article  ADS  Google Scholar 

  30. Wang, C.-R. et al. Enhanced thermoelectric power in dual-gated bilayer graphene. Phys. Rev. Lett. 107, 186602 (2011).

    Article  ADS  Google Scholar 

  31. Duan, J. et al. High thermoelectricpower factor in graphene/hBN devices. Proc. Natl Acad. Sci. USA 113, 14272–14276 (2016).

    Article  ADS  Google Scholar 

  32. Ghahari, F. et al. Enhanced thermoelectric power in graphene: violation of the Mott relation by inelastic scattering. Phys. Rev. Lett. 116, 136802 (2016).

    Article  ADS  Google Scholar 

  33. Mahapatra, P. S. et al. Misorientation-controlled cross-plane thermoelectricity in twisted bilayer graphene. Phys. Rev. Lett. 125, 226802 (2020).

    Article  ADS  Google Scholar 

  34. Ghawri, B. et al. Breakdown of semiclassical description of thermoelectricity in near-magic angle twisted bilayer graphene. Nat. Commun. 13, 1522 (2022).

    Article  ADS  Google Scholar 

  35. Srivastav, S. K. et al. Universal quantized thermal conductance in graphene. Sci. Adv. 5, eaaw5798 (2019).

    Article  ADS  Google Scholar 

  36. Fong, K. C. & Schwab, K. Ultrasensitive and wide-bandwidth thermal measurements of graphene at low temperatures. Phys. Rev. X 2, 031006 (2012).

    Google Scholar 

  37. Crossno, J. et al. Observation of the Dirac fluid and the breakdown of the Wiedemann-Franz law in graphene. Science 351, 1058–1061 (2016).

    Article  ADS  Google Scholar 

  38. Betz, A. C. et al. Supercollision cooling in undoped graphene. Nat. Phys. 9, 109–112 (2013).

    Article  Google Scholar 

  39. Cutler, M. & Mott, N. F. Observation of Anderson localization in an electron gas. Phys. Rev. 181, 1336–1340 (1969).

    Article  ADS  Google Scholar 

  40. Srivastav, S. K. et al. Vanishing thermal equilibration for hole-conjugate fractional quantum Hall states in graphene. Phys. Rev. Lett. 126, 216803 (2021).

    Article  ADS  Google Scholar 

  41. Howson, M. A., Salamon, M. B., Friedmann, T. A., Rice, J. P. & Ginsberg, D. Anomalous peak in the thermopower of YBa2Cu3O7−δ single crystals: a possible fluctuation effect. Phys. Rev. B 41, 300–306 (1990).

    Article  ADS  Google Scholar 

  42. Lu, Y. & Patton, B. R. Fluctuation thermopower above the superconducting transition temperature. J. Phys. Condens. Matter 7, 9247–9254 (1995).

    Article  ADS  Google Scholar 

  43. Uri, A. et al. Mapping the twist-angle disorder and Landau levels in magic-angle graphene. Nature 581, 47–52 (2020).

    Article  ADS  Google Scholar 

  44. Po, H. C., Zou, L., Vishwanath, A. & Senthil, T. Origin of Mott insulating behavior and superconductivity in twisted bilayer graphene. Phys. Rev. X 8, 031089 (2018).

    Google Scholar 

  45. Bultinck, N. et al. Ground state and hidden symmetry of magic-angle graphene at even integer filling. Phys. Rev. X 10, 031034 (2020).

    Google Scholar 

  46. Shavit, G., Berg, E., Stern, A. & Oreg, Y. Theory of correlated insulators and superconductivity in twisted bilayer graphene. Phys. Rev. Lett. 127, 247703 (2021).

    Article  ADS  Google Scholar 

  47. Koshino, M. et al. Maximally localized Wannier orbitals and the extended Hubbard model for twisted bilayer graphene. Phys. Rev. X 8, 031087 (2018).

    Google Scholar 

  48. Moon, P. & Koshino, M. Energy spectrum and quantum Hall effect in twisted bilayer graphene. Phys. Rev. B 85, 195458 (2012).

    Article  ADS  Google Scholar 

  49. Cao, Y. et al. Strange metal in magic-angle graphene with near Planckian dissipation. Phys. Rev. Lett. 124, 076801 (2020).

    Article  ADS  Google Scholar 

  50. Andrei, E. Y. & MacDonald, A. H. Graphene bilayers with a twist. Nat. Mater. 19, 1265–1275 (2020).

    Article  ADS  Google Scholar 

Download references

Acknowledgements

A.D. thanks the Department of Science and Technology (DST) and SERB (DSTO-2051), India for financial support and the MHRD, Government of India under STARS research funding (STARS/APR2019/PS/156/FS), IRPHA(IPA/2020/000034) and also acknowledges the Swarnajayanti Fellowship of the DST/SJF/PSA-03/2018-19. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan and the CREST (JPMJCR15F3), JST.

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Author notes

  1. These authors contributed equally: Arup Kumar Paul, Ayan Ghosh, Souvik Chakraborty.

Authors and Affiliations

  1. Department of Physics, Indian Institute of Science, Bangalore, India

    Arup Kumar Paul, Ayan Ghosh, Souvik Chakraborty, Ujjal Roy, Ranit Dutta, Animesh Panda, Subroto Mukerjee, Sumilan Banerjee & Anindya Das

  2. National Institute for Materials Science, Tsukuba, Japan

    K. Watanabe & T. Taniguchi

  3. Max Planck Institute for the Physics of Complex Systems, Dresden, Germany

    Adhip Agarwala

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Contributions

S.C., A.K.P. and U.R. contributed to device fabrication. A.G. and A.K.P. contributed to data acquisition and analysis. R.D. contributed to initial measurements. A.D. contributed to conceiving the idea and designing the experiment, data interpretation and analysis. K.W. and T.T. synthesized the hBN single crystals. A.P., A.A., S.M. and S.B. contributed to development of theory and data interpretation. All the authors contributed to writing the manuscript.

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Correspondence to Anindya Das.

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Nature Physics thanks Petr Stepanov, Yuanping Chen and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Paul, A.K., Ghosh, A., Chakraborty, S. et al. Interaction-driven giant thermopower in magic-angle twisted bilayer graphene. Nat. Phys. 18, 691–698 (2022). https://doi.org/10.1038/s41567-022-01574-3

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