Mapping quantum Hall edge states in graphene by scanning tunneling microscopy

TL;DR

This study uses scanning tunneling microscopy to map quantum Hall edge states in graphene at high spatial resolution, revealing detailed structures and behaviors of edge states influenced by gate tuning and tip perturbation.

Contribution

It provides the first detailed spatial mapping of quantum Hall edge states in graphene using STM, including effects of tip-induced perturbations and gate tuning.

Findings

Edge states are mapped with minimal perturbation using appropriate gate voltages.

Extended compressible regions and antinodal structures are observed.

Edge states meander along the lateral interface, showing complex patterns.

Abstract

Quantum Hall edge states are the paradigmatic example of the bulk-boundary correspondence. They are prone to intricate reconstructions calling for their detailed investigation at high spatial resolution. Here, we map quantum Hall edge states of monolayer graphene at a magnetic field of 7 T with scanning tunneling microscopy. The graphene sample features a gate-tunable lateral interface between areas of different filling factor. We compare the results with detailed tight-binding calculations quantitatively accounting for the perturbation by the tip-induced quantum dot. We find that the edge state pattern is mapped with little perturbation by adequate choice of gate voltage. We observe extended compressible regions, the antinodal structure of edge states and their meandering along the lateral interface.