Superballistic flow of viscous electron fluid through graphene constrictions*

Electron–electron (e–e) collisions can impact transport in a variety of surprising and sometimes counterintuitive ways. 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. Only recently, sufficiently clean electron systems with transport dominated by e–e collisions have become available [1]. In this talk, we will discuss electron transport through graphene constrictions and show that their conductance below 150 K increases with increasing temperature [2], in contrast to the metallic character of graphene. Notably, the measured conductance exceeds the maximum conductance possible for free electrons. This anomalous behavior is attributed to collective movement of interacting electrons, which ‘shields’ individual carriers from momentum loss at sample boundaries. The measurements allow us to identify the conductance contribution arising due to electron viscosity and determine its temperature dependence.

[1] D. A. Bandurin, et. al., Science 351, 1055 (2016).
[2] R. Krishna Kumar, et. al., Nature Physics in press, (2017).