Suppressed compressibility of quantum Hall effect edge states in epitaxial graphene on SiC

TL;DR

This paper investigates how localized surface states in epitaxial graphene on SiC suppress the formation of compressible stripes at quantum Hall effect edges, contrasting with graphene on insulating substrates.

Contribution

It identifies the role of surface states and charge transfer in suppressing compressible stripes in epitaxial graphene on SiC, a novel insight into edge state behavior.

Findings

Compressible stripes are narrower in G/SiC compared to GraFETs.

Localized surface states cause doping and screening effects.

Suppression of stripe formation is linked to surface state density.

Abstract

We determine conditions for the formation of compressible stripes near the quantum Hall effect (QHE) edges of top-gated epitaxial graphene on Si-terminated SiC (G/SiC) and compare those to graphene exfoliated onto insulating substrate in the field-effect-transistor (GraFET) geometry. For G/SiC, a large density of localised surface states on SiC just underneath graphene layer and charge transfer between them lead both to doping of graphene and to screening of potential profile near its edge. This suppresses formation of compressible stripes near QHE edges in graphene, making them much narrower than the corresponding compressible stripes in GraFETs.