Superballistic flow of viscous electron fluid through graphene constrictions

• Published in: Nature physics 2017-12, Vol.13 (12), p.1182-1185
• Main Authors: Krishna Kumar, R., Bandurin, D. A., Pellegrino, F. M. D., Cao, Y., Principi, A., Guo, H., Auton, G. H., Ben Shalom, M., Ponomarenko, L. A., Falkovich, G., Watanabe, K., Taniguchi, T., Grigorieva, I. V., Levitov, L. S., Polini, M., Geim, A. K.
• Format: Article
• Language: English
• Subjects: 142/126; 639/301/357/918; 639/766/119/995; 639/766/119/999; Atomic; Classical and Continuum Physics; Collisions; Complex Systems; Condensed Matter Physics; Conductance; Constrictions; Electron transport; Electrons; Free electrons; Geometry; Graphene; High temperature; letter; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Resistance; Scattering; Temperature; Temperature dependence; Theoretical; Viscous fluids
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys4240

Graphene systems are clean platforms for studying electron–electron (e–e) collisions. Electron transport in graphene constrictions is now found to behave anomalously due to e–e interactions: conductance values exceed the maximum free-electron value. Electron–electron (e–e) collisions can impact transport in a variety of surprising and sometimes counterintuitive ways 1 , 2 , 3 , 4 , 5 , 6 . Despite strong interest, experiments on the subject proved challenging because of the simultaneous presence of different scattering mechanisms that suppress or obscure consequences of e–e scattering 7 , 8 , 9 , 10 , 11 . Only recently, sufficiently clean electron systems with transport dominated by e–e collisions have become available, showing behaviour characteristic of highly viscous fluids 12 , 13 , 14 . Here we study electron transport through graphene constrictions and show that their conductance below 150 K increases with increasing temperature, in stark contrast to the metallic character of doped graphene 15 . Notably, the measured conductance exceeds the maximum conductance possible for free electrons 16 , 17 . This anomalous behaviour is attributed to collective movement of interacting electrons, which ‘shields’ individual carriers from momentum loss at sample boundaries 18 , 19 . The measurements allow us to identify the conductance contribution arising due to electron viscosity and determine its temperature dependence. Besides fundamental interest, our work shows that viscous effects can facilitate high-mobility transport at elevated temperatures, a potentially useful behaviour for designing graphene-based devices.