Coulomb Drag Mechanisms in Graphene

TL;DR

This paper explains anomalous Coulomb drag in graphene through a new energy transport mechanism involving interlayer energy transfer and thermopower, accounting for giant enhancements and magnetic field sensitivity.

Contribution

It introduces a novel energy transport-based mechanism for Coulomb drag in graphene, distinct from traditional charge transfer explanations.

Findings

Energy transport dominates Coulomb drag near charge neutrality.

The new mechanism accounts for giant drag enhancement and sign reversal.

Drag becomes independent of electron-electron interaction strength under realistic conditions.

Abstract

Recent measurements revealed an anomalous Coulomb drag in graphene, hinting at new physics at charge neutrality. The anomalous drag is explained by a new mechanism based on energy transport, which involves interlayer energy transfer, coupled to charge flow via lateral heat currents and thermopower. The old and new drag mechanisms are governed by distinct physical effects, resulting in starkly different behavior, in particular for drag magnitude and sign near charge neutrality. The new mechanism explains the giant enhancement of drag near charge neutrality, as well as its sign and anomalous sensitivity to magnetic field. Under realistic conditions, energy transport dominates in a wide temperature range, giving rise to a universal value of drag which is essentially independent of the electron-electron interaction strength.