Hydrodynamic transport and the shear viscosity of 2D quantum electron liquids
Prof. Dr. Marco Polini (Istituto Italiano di Tecnologia, Graphene Labs, Genova, Italy)

Transport in strongly interacting electron liquids is described by the laws of hydrodynamics. In the hydrodynamic regime electron-electron collisions are so frequent that the electron liquid is well described by a quasi-equilibrium distribution function characterized by slowly-varying time-dependent density and drift velocity, the local counterparts of globally conserved particle number and momentum.
Transport coefficients such as the hydrodynamic shear viscosity and the thermal conductivity play therefore a pivotal role in this intriguing regime.
It is believed that the shear viscosity of strongly interacting quantum fluids such as the quark-gluon plasma and ultracold atomic Fermi gases in the unitarity limit can be accurately measured.
On the contrary, no experimental data exist, to the best of our knowledge, on the shear viscosity of two-dimensional quantum electron liquids hosted in a solid-state matrix.
In this Theoriekolloquium I will discuss fully-electrical viscometers for 2D quantum electron liquids [1,2]. I will also present recent results showing robust evidence of viscous-dominated hydrodynamic flow in ultra-clean graphene sheets encapsulated between hexagonal boron nitride slabs [3].

[1] A. Tomadin, G. Vignale, and M. Polini, Phys. Rev. Lett. 113, 235901 (2014).
[2] I. Torre, A. Tomadin, A.K. Geim, and M. Polini, Phys. Rev. B 92, 165433 (2015).
[3] D.A. Bandurin, I. Torre, R. Krishna Kumar, M. Ben Shalom, A. Tomadin, A. Principi, G.H. Auton, E. Khestanova, K.S. Novoselov, I.V. Grigorieva, L.A. Ponomarenko, A.K. Geim, and M. Polini, arXiv:1509.04165 (2015).