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SUMMARY:Electron Hydrodynamics in Graphene: Fundamentals and Application -
  Denis Bandurin\, School of Physics &amp\; Astronomy\, University of Manch
 ester\, Manchester M13 9PL\, United Kingdom
DTSTART:20180604T131500Z
DTEND:20180604T141500Z
UID:TALK104467@talks.cam.ac.uk
CONTACT:Dr Joanna Waldie
DESCRIPTION:Transport in systems with many particles experiencing frequent
  mutual collisions (such as gases or liquids) has been studied for more th
 an two centuries and is accurately described by the theory of hydrodynamic
 s. It has been argued theoretically for a long time that the collective be
 haviour of charge carriers in solids can also be treated by the hydrodynam
 ic approach. However\, despite many attempts\, very little evidence of hyd
 rodynamic electron transport has been found so far.\n\nGraphene encapsulat
 ed between hexagonal boron nitride (hBN) offers an ideal platform to study
  electron hydrodynamics as it hosts an ultra-clean electronic system with 
 electron-electron collisions being the dominant scattering source above li
 quid nitrogen temperatures. In the first part of my talk we will discuss w
 hy electron hydrodynamics has not been observed before and how it manifest
 s itself in electron transport. Furthermore\, it will be shown that electr
 ons in graphene can behave as a very viscous fluid (more viscous than hone
 y) forming vortices of applied electron current [1]. In the second part\, 
 we will discuss the measurements of the viscosity of an electron fluid by 
 its superballistic flow through graphene point contacts [2]. Then we will 
 talk about the behaviour of electron fluids in the presence of magnetic fi
 eld where I will report the experimental measurements of the Hall viscosit
 y in two dimensions [3]. This dissipationless transport coefficient has be
 en widely discussed in theoretical literature on fluid mechanics\, plasma 
 physics and condensed matter physics\, yet\, until now\, any experimental 
 evidence has been lacking\, making the phenomenon truly a unicorn. Last bu
 t not least\, we will discuss how electron hydrodynamics can be used for t
 he development of terahertz photodetectors where I report some recent prog
 ress in this direction [4].\n\n[1] Negative Local Resistance Caused by Vis
 cous Electron Backflow in Graphene\, D. A. Bandurin\, A. Principi\, G.H. A
 uton\, E. Khestanova\, K.S. Novoselov\, I. V Grigorieva\, L.A. Ponomarenko
 \, A.K. Geim\, and M. Polini\, Science 351\, 1055 (2016).\n\n[2] Superball
 istic Flow of Viscous Electron Fluid through Graphene Constrictions\, R. K
 rishna 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\, Nat. Phys. 13\
 , 1182 (2017).\n\n[3] Measuring Hall viscosity of Graphene’s Electron Fl
 uid\, I. Berdyugin\, S. G. Xu\, F. M. D. Pellegrino\, R. Krishna Kumar\, A
 . Principi\, I. Torre\, M. Ben Shalom\, T. Taniguchi\, K. Watanabe\, I. V.
  Grigorieva\, M. Polini\, A. K. Geim and D. A. Bandurin\, to appear on arx
 iv soon.\n\n[4] Dual Origin of Room Temperature Sub-terahertz Photorespons
 e in Graphene Field Effect Transistors\, D. A. Bandurin\, I. Gayduchenko\,
  Y. Cao\, M. Moskotin\, A. Principi\, I. V. Grigorieva\, G. Goltsman\, G. 
 Fedorov\, and D. Svintsov\, Appl. Phys. Lett. 112\, 141101 (2018).
LOCATION:Mott Seminar Room (Mott Building Room 531)\, Cavendish Laboratory
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