title: Negative local resistance caused by viscous electron backflow in graphene.
abstract: Graphene hosts a unique electron system in which electron-phonon scattering is extremely weak but electron-electron collisions are sufficiently frequent to provide local equilibrium above the temperature of liquid nitrogen. Under these conditions, electrons can behave as a viscous liquid and exhibit hydrodynamic phenomena similar to classical liquids. Here we report strong evidence for this transport regime. We found that doped graphene exhibits an anomalous (negative) voltage drop near current-injection contacts, which is attributed to the formation of submicrometer-size whirlpools in the electron flow. The viscosity of graphene's electron liquid is found to be ~0.1 square meters per second, an order of magnitude higher than that of honey, in agreement with many-body theory. Our work demonstrates the possibility of studying electron hydrodynamics using high-quality graphene.
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: D A
authors.initials: DA
authors.lastname: Bandurin
authors.affiliation: National Enterprise for nanoScience and nanoTechnology, Scuola Normale Superiore, I-56126 Pisa, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Torre
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK. Department of Physics, Lancaster University, Lancaster LA14YB, UK.
authors.forename: R
authors.initials: R
authors.lastname: Krishna Kumar
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK. National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: M
authors.initials: M
authors.lastname: Ben Shalom
authors.affiliation: National Enterprise for nanoScience and nanoTechnology, Istituto Nanoscienze-Consiglio Nazionale delle Ricerche and Scuola Normale Superiore, I-56126 Pisa, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Tomadin
authors.affiliation: Institute for Molecules and Materials, Radboud University, NL-6525 AJ Nijmegen, Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Principi
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: G H
authors.initials: GH
authors.lastname: Auton
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK. National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: E
authors.initials: E
authors.lastname: Khestanova
authors.affiliation: National Graphene Institute, University of Manchester, Manchester M13 9PL, UK.
authors.forename: K S
authors.initials: KS
authors.lastname: Novoselov
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: I V
authors.initials: IV
authors.lastname: Grigorieva
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK. Department of Physics, Lancaster University, Lancaster LA14YB, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Ponomarenko
authors.affiliation: School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
authors.forename: A K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, I-16163 Genova, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Polini