Upstream modes and antidots poison graphene quantum Hall effect

TL;DR

This paper investigates how antidots along graphene edges cause backscattering and topological breakdown in the quantum Hall effect, using scanning gate microscopy and simulations to understand the channels' vulnerability.

Contribution

It demonstrates the detrimental role of antidots in graphene edge channels and provides insights into their impact on topological protection in the quantum Hall regime.

Findings

Antidots mediate backscattering in graphene edge channels.

Scanning gate microscopy reveals local breakdown mechanisms.

Simulations support experimental observations.

Abstract

The quantum Hall effect is the seminal example of topological protection, as charge carriers are transmitted through one-dimensional edge channels where backscattering is prohibited. Graphene has made its marks as an exceptional platform to reveal new facets of this remarkable property. However, in conventional Hall bar geometries, topological protection of graphene edge channels is found regrettably less robust than in high mobility semi-conductors. Here, we explore graphene quantum Hall regime at the local scale, using a scanning gate microscope. We reveal the detrimental influence of antidots along the graphene edges, mediating backscattering towards upstream edge channels, hence triggering topological breakdown. Combined with simulations, our experimental results provide further insights into graphene quantum Hall channels vulnerability. In turn, this may ease future developments towards precise manipulation of topologically protected edge channels hosted in various types of two-dimensional crystals.