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Ju L, Shi Z, Nair N, et al. Topological valley transport at bilayer graphene domain walls. Nature. 2015;520(7549):650-5doi: 10.1038/nature14364.
Ju, L., Shi, Z., Nair, N., Lv, Y., Jin, C., Velasco, J., Ojeda-Aristizabal, C., Bechtel, H. A., Martin, M. C., Zettl, A., Analytis, J., & Wang, F. (2015). Topological valley transport at bilayer graphene domain walls. Nature, 520(7549), 650-5. https://doi.org/10.1038/nature14364
Ju, Long, et al. "Topological valley transport at bilayer graphene domain walls." Nature vol. 520,7549 (2015): 650-5. doi: https://doi.org/10.1038/nature14364
Ju L, Shi Z, Nair N, Lv Y, Jin C, Velasco J, Ojeda-Aristizabal C, Bechtel HA, Martin MC, Zettl A, Analytis J, Wang F. Topological valley transport at bilayer graphene domain walls. Nature. 2015 Apr 30;520(7549):650-5. doi: 10.1038/nature14364. Epub 2015 Apr 22. PMID: 25901686.
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Nature. 2015 Apr 30;520(7549):650-5. doi: 10.1038/nature14364. Epub 2015 Apr 22.

Topological valley transport at bilayer graphene domain walls.

Nature

Long Ju, Zhiwen Shi, Nityan Nair, Yinchuan Lv, Chenhao Jin, Jairo Velasco, Claudia Ojeda-Aristizabal, Hans A Bechtel, Michael C Martin, Alex Zettl, James Analytis, Feng Wang

Affiliations

  1. Department of Physics, University of California, Berkeley, California 94720, USA.
  2. Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
  3. 1] Department of Physics, University of California, Berkeley, California 94720, USA [2] Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [3] Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.

PMID: 25901686 DOI: 10.1038/nature14364

Abstract

Electron valley, a degree of freedom that is analogous to spin, can lead to novel topological phases in bilayer graphene. A tunable bandgap can be induced in bilayer graphene by an external electric field, and such gapped bilayer graphene is predicted to be a topological insulating phase protected by no-valley mixing symmetry, featuring quantum valley Hall effects and chiral edge states. Observation of such chiral edge states, however, is challenging because inter-valley scattering is induced by atomic-scale defects at real bilayer graphene edges. Recent theoretical work has shown that domain walls between AB- and BA-stacked bilayer graphene can support protected chiral edge states of quantum valley Hall insulators. Here we report an experimental observation of ballistic (that is, with no scattering of electrons) conducting channels at bilayer graphene domain walls. We employ near-field infrared nanometre-scale microscopy (nanoscopy) to image in situ bilayer graphene layer-stacking domain walls on device substrates, and we fabricate dual-gated field effect transistors based on the domain walls. Unlike single-domain bilayer graphene, which shows gapped insulating behaviour under a vertical electrical field, bilayer graphene domain walls feature one-dimensional valley-polarized conducting channels with a ballistic length of about 400 nanometres at 4 kelvin. Such topologically protected one-dimensional chiral states at bilayer graphene domain walls open up opportunities for exploring unique topological phases and valley physics in graphene.

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