Anti-Poiseuille flow in neutral graphene

TL;DR

This paper investigates the unique hydrodynamic energy flow in neutral graphene, revealing that classical Poiseuille flow cannot be driven by electric fields but can be observed through nonuniform current densities influenced by boundary scattering and magnetic fields.

Contribution

It demonstrates the absence of Poiseuille flow driven by electric fields in neutral graphene and explores how boundary conditions and magnetic fields affect current density profiles.

Findings

Poiseuille flow cannot be driven by electric fields in neutral graphene.

Nonuniform current densities can be observed via boundary scattering and magnetic fields.

Current profile curvature is influenced by supercollision processes.

Abstract

Hydrodynamic flow of charge carriers in graphene is an energy flow unlike the usual mass flow in conventional fluids. In neutral graphene, the energy flow is decoupled from the electric current, making it difficult to observe the hydrodynamic effects and measure the viscosity of the electronic fluid by means of electric current measurements. In particular, we show that the hallmark Poiseuille flow in a narrow channel cannot be driven by the electric field irrespective of boundary conditions at the channel edges. Nevertheless one can observe nonuniform current densities similarly to the case of the well-known ballistic-diffusive crossover. The standard diffusive behavior with the uniform current density across the channel is achieved under the assumptions of specular scattering on the channel boundaries. This flow can also be made nonuniform by applying weak magnetic fields. In this case, the curvature of the current density profile is determined by the quasiparticle recombination processes dominated by the disorder-assisted electron-phonon scattering -- the so-called supercollisions.