Uploaded October 2022 | Updated September 2026, 2 weeks ago
Prof. Giovanni Vignale
Institute for Intelligent Functional Materials (I-FIM), National University of Singapore
ABSTRACT:
Electric and thermal transport in electronic systems has long been described in terms of an independent-particle picture (Landau theory of Fermi liquids) which emphasizes the role of collisions between electrons and impurities or lattice vibrations, with electron-electron collisions playing a secondary role. It is only in the past two decades that advances in the fabrication of ultra clean samples have refocused the interest on collective hydrodynamic transport - a transport regime which is controlled by the nearly conserved quantities: particle number, momentum, and energy density, and by electron-electron interactions tying their values together. In this talk I review some of the recent theoretical and experimental progress in our understanding of electronic hydrodynamics in graphene-based materials. Several novel effects have been predicted and experimentally observed, including large deviations from the conventional Wiedemann-Franz law, which connects the electric and thermal conductivities. I then move on to other realizations of hydrodynamic concepts, namely in Fermionic cold atoms and in the quark-gluon plasma of quantum chromodynamics. In the latter case I review the theoretical arguments, based on holographic duality and supported by experiment, which suggests that the quark-gluon plasma should be an almost perfect fluid, with a viscosity to entropy ratio close to a conjectured lower bound ℏ⁄(4πk_B ), which, quite surprisingly, is also approached by electrons in pristine graphene.
Prof. Giovanni Vignale
Institute for Intelligent Functional Materials (I-FIM), National University of Singapore
ABSTRACT:
Electric and thermal transport in electronic systems has long been described in terms of an independent-particle picture (Landau theory of Fermi liquids) which emphasizes the role of collisions between electrons and impurities or lattice vibrations, with electron-electron collisions playing a secondary role. It is only in the past two decades that advances in the fabrication of ultra clean samples have refocused the interest on collective hydrodynamic transport - a transport regime which is controlled by the nearly conserved quantities: particle number, momentum, and energy density, and by electron-electron interactions tying their values together. In this talk I review some of the recent theoretical and experimental progress in our understanding of electronic hydrodynamics in graphene-based materials. Several novel effects have been predicted and experimentally observed, including large deviations from the conventional Wiedemann-Franz law, which connects the electric and thermal conductivities. I then move on to other realizations of hydrodynamic concepts, namely in Fermionic cold atoms and in the quark-gluon plasma of quantum chromodynamics. In the latter case I review the theoretical arguments, based on holographic duality and supported by experiment, which suggests that the quark-gluon plasma should be an almost perfect fluid, with a viscosity to entropy ratio close to a conjectured lower bound ℏ⁄(4πk_B ), which, quite surprisingly, is also approached by electrons in pristine graphene.
