Upstream modes and antidots poison graphene quantum Hall effect

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• The quantum Hall effect exemplifies topological protection, utilizing 1D edge channels that prevent backscattering.
• Graphene is a promising material for studying topological properties, but its edge channels show less robustness than in semiconductors.
• Conventional Hall bar geometries limit the understanding of graphene's quantum Hall regime.

Purpose of the Study:

• To investigate the local-scale behavior of graphene's quantum Hall regime.
• To identify factors affecting the robustness of topological protection in graphene edge channels.
• To understand the influence of edge imperfections on topological breakdown.

Main Methods:

• Utilizing a scanning gate microscope to probe the graphene quantum Hall regime at a local scale.
• Conducting experiments on graphene Hall bar geometries with edge antidots.
• Employing computational simulations to complement experimental findings.

Main Results:

• Antidots along graphene edges were found to mediate backscattering towards upstream edge channels.
• This backscattering triggers a breakdown of topological protection in the quantum Hall regime.
• The local-scale exploration revealed specific vulnerabilities in graphene's edge channels.

Conclusions:

• Experimental and simulation results highlight the detrimental effect of antidots on graphene's topological protection.
• Understanding these vulnerabilities is crucial for future advancements in manipulating topologically protected edge channels.
• This research provides insights applicable to various two-dimensional crystalline materials.