Attività del Dipartimento

Colloqui di Fisica

Viscous electron transport

Marco Polini

08-05-2018 - 15:00
AULA B - Via Della Vasca Navale 84


Frequent collisions between constituents in a classical or quantum liquid (like 3He) manifest through a transport coefficient called the shear viscosity [1]. The flow of these liquids, and also that of exotic quantum many-particle systems like ultracold 6Li atoms near a Feshbach resonance [2] and quark-gluon plasmas at relativistic heavy-ion colliders [3], is often described by three equations expressing the conservation of mass, momentum (the Navier-Stokes equation), and energy.
Realizing hydrodynamic transport in a solid has proven challenging, because of ever present processes that lead to momentum dissipation in the electron subsystem [4]. Even when suitable conditions are met, key questions have remained largely unexplored: how do you diagnose the emergence of hydrodynamic electron flow in a conventional field-effect transistor? How do you measure the viscosity of an electron liquid in such a setup? What is the impact of viscosity on electron transport?
In this Colloquium I will try and answer these questions. I will first report on results of combined theoretical and experimental work [5,6,7] showing unambiguous evidence for the long-sought hydrodynamic solid-state transport regime. In particular, I will discuss how high-quality doped graphene sheets above liquid nitrogen temperatures exhibit negative non-local resistance near current injection points and whirlpools in the spatial current pattern [5,6,7]. Measurements of these non-local electrical signals allow to extract the value of the kinematic viscosity of the two-dimensional electron liquid in graphene, which is found to be an order of magnitude larger than that of honey and to compare well with many-body theoretical predictions [8]. I will then discuss viscous electron transport across a point contact [9] and ideas on how to probe hydrodynamic behavior via the use of engineered short-wavelength plasmon-phonon polaritons in hybrid stacks containing graphene, Boron Nitride, and metal gates [10].

[1] J.C.Maxwell, Philos. Trans. R. Soc. London 156, 249 (1866). 

[2] C. Cao, E. Elliott, J. Joseph, H. Wu, J. Petricka, T. Schäfer, and J.E. Thomas, Science 331, 58 (2011).
[3] B.V. Jacak and B. Müller, Science 337, 310 (2012).
[4] R.N. Gurzhi, Sov. Phys. Uspekhi 11, 255 (1968).
[5] I. Torre, A. Tomadin, A.K. Geim, and M. Polini, Phys. Rev. B 92, 165433 (2015).
[6] D. Bandurin, I. Torre, R.K. Kumar, M. Ben Shalom, A. Tomadin, A. Principi, G.H. Auton, E. Khestanova, K.S. NovoseIov, I.V. Grigorieva, L.A. Ponomarenko, A.K. Geim, and M. Polini, Science 351, 1055 (2016).
[7] F.M.D. Pellegrino, I. Torre, A.K. Geim, and M. Polini, Phys. Rev. B 94, 155414 (2016).
[8] A. Principi, G. Vignale, M. Carrega, and M. Polini, Phys. Rev. B 93, 125410 (2016).
[9] R.K. Kumar, D.A. Bandurin, F.M.D. Pellegrino, Y. Cao, A. Principi, H. Guo, G.H. Auton, M. Ben Shalom, L.A. Ponomarenko, G. Falkovich, I.V. Grigorieva, L.S. Levitov, M. Polini, and A.K. Geim, Nature Phys. 13, 1182 (2017).
[10] M.B. Lundeberg, Y. Gao, R. Asgari, C. Tan, B. Van Duppen, M. Autore, P. Alonso-Gonzalez, A. Woessner, K. Watanabe, T. Taniguchi, R. Hillenbrand, J. Hone, M. Polini, and F.H.L. Koppens, Science 357, 187 (2017).


org: MELONI Davide

Allegati: [locandina]  


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