Friction force on slow charges moving over supported graphene

TL;DR

This paper presents a theoretical model for the dielectric interaction between slow-moving charges and supported graphene, highlighting the effects of substrate response, phonon excitations, and hybridization phenomena on friction and stopping forces.

Contribution

It introduces a combined dielectric model of graphene and substrate using RPA and non-local response, analyzing low-frequency excitations and their impact on friction and stopping forces.

Findings

Identification of hybridization between graphene pi plasmon and substrate phonon.

Estimation of damping rate in graphene from HREELS data.

Demonstration of substrate influence on friction coefficient for slow charges.

Abstract

We provide a theoretical model that describes the dielectric coupling of a 2D layer of graphene, represented by a polarization function in the Random Phase Approximation, and a semi-infinite 3D substrate, represented by a surface response function in a non-local formulation. We concentrate on the role of the dynamic response of the substrate for low-frequency excitations of the combined graphene-substrate system, which give rise to the stopping force on slowly moving charges above graphene. A comparison of the dielectric loss function with experimental HREELS data for graphene on a SiC substrate is used to estimate the damping rate in graphene and to reveal the importance of phonon excitations in an insulating substrate. A signature of the hybridization between graphene's pi plasmon and the substrate's phonon is found in the stopping force. A friction coefficient that is calculated for slow charges moving above graphene on a metallic substrate shows an interplay between the low-energy single-particle excitations in both systems.