Counterflows in viscous electron-hole fluid

TL;DR

This paper explores how viscous electron-hole fluids in ultra-pure conductors exhibit counterflows and edge currents under magnetic fields, revealing complex flow patterns similar to viscous fluids.

Contribution

It demonstrates the emergence of counterflows and non-trivial edge current profiles due to viscosity and recombination in hydrodynamic electron-hole systems.

Findings

Counterflows appear due to viscosity and recombination effects.

Edge currents form two stripe-like regions with opposite flow directions.

Flow profiles are non-trivial and spatially complex.

Abstract

In ultra-pure conductors, collective motion of charge carriers at relatively high temperatures may become hydrodynamic such that electronic transport may be described similarly to a viscous flow. In confined geometries (e.g., in ultra-high quality nanostructures), the resulting flow is Poiseuille-like. When subjected to a strong external magnetic field, the electric current in semimetals is pushed out of the bulk of the sample towards the edges. Moreover, we show that the interplay between viscosity and fast recombination leads to the appearance of counterflows. The edge currents possess a non-trivial spatial profile and consist of two stripe-like regions: the outer stripe carrying most of the current in the direction of the external electric field and the inner stripe with the counterflow.