Dragging of electric current by hydrodynamic flow at charge neutrality

TL;DR

This paper develops a hydrodynamic theory of Coulomb drag in graphene double layers near charge neutrality, revealing nonmonotonic behavior and sign changes in drag resistivity due to interlayer correlations and disorder effects.

Contribution

It introduces a comprehensive hydrodynamic model accounting for disorder correlations, predicting novel nonmonotonic and sign-changing drag phenomena in graphene double layers.

Findings

Drag resistivity shows nonmonotonic dependence on carrier density.

Sign change of drag resistivity occurs with symmetric doping.

Quantitative estimates provided for graphene double-layer devices.

Abstract

We develop a theory of drag in graphene double layers near charge neutrality. We work in the regime of electron hydrodynamics and account for interlayer correlations of charge puddle disorder. The drag resistivity is expressed in terms of the viscosity, intrinsic conductivity of the electron liquid, and the correlation function of the puddle disorder. The contributions of the interlayer transfer of momentum and energy to drag have opposite signs. This leads to a nonmonotonic dependence of the drag resistivity on the carrier density. For layer-symmetric doping, the drag resistivity changes sign as a function of the carrier density. At interlayer separations shorter than the disorder correlation length, the transconductivity saturates to the disorder-induced enhancement of the intralayer conductivity. We provide quantitative estimates of the effect for Dirac electron liquids in monolayer graphene and bilayer graphene double-layer devices.