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Close to the Dirac point, graphene is expected to exist in a quantum critical Dirac fluid state, where the flow of both charge and heat can be described with a characteristic d.c. electrical conductivity and thermodynamic variables such as entropy and enthalpy densities. Although the fluid-like viscous flow of charge has been reported in state-of-the-art graphene devices, the value of conductivity, predicted to be quantized and determined only by the universality class of the critical point, has not been established experimentally so far. Here we have discerned the quantum critical universality in graphene transport by combining the electrical and thermal conductivities in very high-quality devices close to the Dirac point. We find that they are inversely related, as expected from relativistic hydrodynamics, and the characteristic conductivity converges to a quantized value. We also observe a giant violation of the Wiedemann–Franz law, where the Lorentz number exceeds the semiclassical value by more than 200 times close to the Dirac point at low temperatures. At high temperatures, the effective dynamic viscosity to entropy density ratio close to the Dirac point in the cleanest devices approaches that of a minimally viscous quantum fluid within a factor of four.

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• In Copyright
  

  This version of the article has been accepted for publication, after peer review (when applicable) and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at: https://doi.org/10.1038/s41567-025-02972-z.

Keyword: Graphene, Quantum critical Dirac fluid, Wiedemann–Franz law

Date published: 2025-08-13

Publisher: Springer Science and Business Media LLC

Journal:

• Nature Physics (ISSN: 17452481) vol. 21 issue. 9 p. 1374-1379

Funding:

• Ministry of Human Resource Development PMRF
• Ministry of Human Resource Development PMRF
• MEXT | Japan Society for the Promotion of Science 21H05233, 23H0205
• MEXT | Japan Society for the Promotion of Science 21H05233, 23H0205
• World Premier International Research Center Initiative (WPI), MEXT, Japan
• Department of Science and Technology, Ministry of Science and Technology Nanomission
• JC Bose Fellowship

Manuscript type: Author's version (Accepted manuscript)

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First published URL: https://doi.org/10.1038/s41567-025-02972-z

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Updated at: 2026-07-03 13:24:12 +0900

Published on MDR: 2026-07-03 14:29:37 +0900