Quantized edge modes in atomic-scale point contacts in graphene

Abstract

The zigzag edges of single- or few-layer graphene are perfect one-dimensional conductors owing to a set of gapless states that are topologically protected against backscattering. Direct experimental evidence of these states has been limited so far to their local thermodynamic and magnetic properties, determined by the competing effects of edge topology and electron–electron interaction. However, experimental signatures of edge-bound electrical conduction have remained elusive, primarily due to the lack of graphitic nanostructures with low structural and/or chemical edge disorder. Here, we report the experimental detection of edge-mode electrical transport in suspended atomic-scale constrictions of single and multilayer graphene created during nanomechanical exfoliation of highly oriented pyrolytic graphite. The edge-mode transport leads to the observed quantization of conductance close to multiples of G0 = 2e2/h. At the same time, conductance plateaux at G0/2 and a split zero-bias anomaly in non-equilibrium transport suggest conduction via spin-polarized states in the presence of an electron–electron interaction.

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Figure 1: Mechanical exfoliation process and corresponding evolution of electrical conductance.
Figure 2: Non-equilibrium transport and magneto-conductance in nanoconstrictions.
Figure 3: Fractional quantization of the zero-bias conductance.

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Acknowledgements

The authors acknowledge financial support from the Department of Science and Technology, Government of India. A.A. acknowledges support from CSIR, India, through a senior research fellowship. S.S. acknowledges support from the National Science Foundation (DMR-1508680).

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Contributions

A.K. and A.G. conceived and designed the experiments. A.K., T.P.S. and S.B. performed the experiments. A.K., T.P.S., S.B., A.A., T.B., H.R.K., M.J., V.B.S. and A.G. analysed the data. A.A., T.B., S.K.S., H.R.K., M.J. and V.B.S. carried out theoretical modelling and calculations. T.P.S., M.J., V.B.S. and A.G. co-wrote the paper.

Corresponding authors

Correspondence to Amogh Kinikar or T. Phanindra Sai or Arindam Ghosh.

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The authors declare no competing financial interests.

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Kinikar, A., Phanindra Sai, T., Bhattacharyya, S. et al. Quantized edge modes in atomic-scale point contacts in graphene. Nature Nanotech 12, 564–568 (2017). https://doi.org/10.1038/nnano.2017.24

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