Direct imaging of topological edge states at a bilayer graphene domain wall.

Long-Jing Yin,Lin He,Hua Jiang,Jia-Bin Qiao

doi:10.1038/ncomms11760

Long-Jing Yin, Lin He + Show 2 more

Open Access

https://doi.org/10.1038/ncomms11760

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Abstract

The AB–BA domain wall in gapped graphene bilayers is a rare naked structure hosting topological electronic states. Although it has been extensively studied in theory, a direct imaging of its topological edge states is still missing. Here we image the topological edge states at the graphene bilayer domain wall by using scanning tunnelling microscope. The simultaneously obtained atomic-resolution images of the domain wall provide us unprecedented opportunities to measure the spatially varying edge states within it. The one-dimensional conducting channels are observed to be mainly located around the two edges of the domain wall, which is reproduced quite well by our theoretical calculations. Our experiment further demonstrates that the one-dimensional topological states are quite robust even in the presence of high magnetic fields. The result reported here may raise hopes of graphene-based electronics with ultra-low dissipation.

Highlights

The AB–BA domain wall in gapped graphene bilayers is a rare naked structure hosting topological electronic states
The decoupled bilayer graphene on graphite exhibits a small period of moirepatterns in the scanning tunnelling microscopy (STM) measurements[19,21,25] and its atomic-resolution STM image shows a triangular lattice because of the A/B atoms’ asymmetry in the topmost Bernal bilayer
We attribute the 1D structure in Fig. 1c to the AB–BA domain wall in bilayer graphene

Summary

Introduction

The AB–BA domain wall in gapped graphene bilayers is a rare naked structure hosting topological electronic states It has been extensively studied in theory, a direct imaging of its topological edge states is still missing. The AB–BA domain wall in graphene bilayer, with electrons residing right at the surface, provides unprecedented opportunities to directly image the topologically protected 1D conducting channels. Such a crystalline topological line defect exists naturally in Bernal graphene bilayers grown by chemical vapour deposition[16,17] and in exfoliated bilayer graphene (that is, prepared using adhesive tape) from graphite[13]. The exfoliated bilayer and trilayer graphene flakes were deposited on the substrate (here the supporting substrate is graphite) during the process of mechanical exfoliation and, very importantly, these graphene sheets decouple from the graphite surface due to the presence of the stacking misorientation with the underlying substrates, as demonstrated in this study and in previous studies[18,19,20,21,22,23,24,25]

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