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

Understand

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, due to decoupling of charge and heat currents within hydrodynamics.
• Employing high sensitivity Johnson noise thermometry, we report the breakdown of the Wiedemann-Franz law in graphene, with a thermal conductivity an order of magnitude larger than the value predicted by Fermi liquid theory.