Negative Viscosity and Eddy Flow of Imbalanced Electron-Hole Liquid in Graphene

TL;DR

This paper develops a hydrodynamic model for electron-hole liquids in graphene, revealing that imbalance relaxation can lead to negative viscosity and swirling eddy flows, affecting nonlocal resistivity patterns.

Contribution

It introduces a novel hydrodynamic framework accounting for imbalance relaxation, predicting negative viscosity and eddy flow phenomena in graphene.

Findings

Negative effective viscosity near charge neutrality.

Emergent eddy flow pattern of swirling currents.

Nonlocal resistivity oscillations due to eddy flows.

Abstract

We present a hydrodynamic theory for electron-hole magnetotransport in graphene incorporating carrier-population imbalance, energy, and momentum relaxation processes. We focus on the electric response and find that the carrier and energy imbalance relaxation processes strongly modify the shear viscosity, so that an effective viscosity can be negative in the vicinity of charge neutrality. We predict an emergent eddy flow pattern of swirling currents and explore its manifestation in nonlocal resistivity oscillations in a strip of graphene driven by a source current.