Observation of the Dirac fluid and the breakdown of the Wiedemann-Franz law in graphene

By J. Crossno, Jing Shi, Ke Wang, Xiaomeng Liu, Achim Harzheim, Andrew Lucas, Subir Sachdev, Philip Kim, Takashi Taniguchi, Kenji Watanabe and 2 more. Science, 2015

636 citations recorded by the source corpus.

Electrons that flow like a fluid Electrons inside a conductor are often described as flowing in response to an electric field. This flow rarely resembles anything like the familiar flow of water through a pipe, but three groups describe counterexamples (see the Perspective by Zaanen). Moll et al. found that the viscosity of the electron fluid in thin wires of PdCoO2 had a major effect on the flow, much like what happens in regular fluids. Bandurin et al. found evidence in graphene of electron whirlpools similar to those formed by viscous fluid flowing through a small opening. Finally, Crossno et al. observed a huge increase of thermal transport in graphene, a signature of so-called Dirac fluids. Science, this issue p. 1061, 1055, 1058; see also p. 1026 Thermal transport is enhanced near the charge-neutrality point in graphene, owing to the dominant interelectron interactions. [Also see Perspective by Zaanen] Interactions between particles in quantum many-body systems can lead to collective behavior described by hydrodynamics. One such system is the electron-hole plasma in graphene near the charge-neutrality point, which can form a strongly coupled Dirac fluid. This charge-neutral plasma of quasi-relativistic fermions is expected to exhibit a substantial enhancement of the thermal conductivity, thanks to decoupling of charge and heat currents within hydrodynamics. Employing high-sensitivity Johnson noise thermometry, we report an order of magnitude increase in the thermal conductivity and the breakdown of the Wiedemann-Franz law in the thermally populated charge-neutral plasma in graphene. This result is a signature of the Dirac fluid and constitutes direct evidence of collective motion in a quantum electronic fluid.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/39607475be0913ea610b556a56c766e2a8ce41b0

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Citations in the corpus

Notes on Anomaly Induced Transport (2016, background): “Viscous flow of the electron fluid in Graphene has recently been measured [113, 114, 115].”
Lecture notes on Generalised Hydrodynamics (2019, background): “[13, 14], as well as the large amount of progress done in the context of electron flows in graphene-based systems [15, 16, 17, 18], which has had experimental evidence [19, 20, 21].”
Relativistic magnetohydrodynamics (2017, background): “Examples include transport near relativistic quantum critical points [12], in graphene [13, 14] and in Weyl semi-metals [15].”
Holographic Quantum Matter (2016, background): “such as viscosity, compared to global transport measurements [152].”
Fracton hydrodynamics (2020, background): “[5] J.”
Polaritons in van der Waals materials (2016, background): “Ultrafast heating of electrons and plasmons may realize a regime in which the dynamics of an approximately equal number of electrons and holes in graphene resembles the behavior of viscous liquids described by relativistic hydrodynamics (34, 35).”