Edge currents shunt the insulating bulk in gapped graphene

Zhu, M. J. and Kretinin, A. V. and Thompson, Michael Dermot and Bandurin, D. A. and Hu, S. and Yu, G. L. and Birkbeck, J. and Mishchenko, Artem and Vera-Marun, I. J. and Watanabe, K. and Taniguchi, T. and Polini, M. and Prance, Jonathan Robert and Novoselov, K. S. and Geim, A. K. and Ben Shalom, M. (2017) Edge currents shunt the insulating bulk in gapped graphene. Nature Communications, 8. ISSN 2041-1723

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An energy gap can be opened in the spectrum of graphene reaching values as large as 0.2 eV in the case of bilayers. However, such gaps rarely lead to the highly insulating state expected at low temperatures. This long-standing puzzle is usually explained by charge inhomogeneity. Here we revisit the issue by investigating proximity-induced superconductivity in gapped graphene and comparing normal-state measurements in the Hall bar and Corbino geometries. We find that the supercurrent at the charge neutrality point in gapped graphene propagates along narrow channels near the edges. This observation is corroborated by using the edgeless Corbino geometry in which case resistivity at the neutrality point increases exponentially with increasing the gap, as expected for an ordinary semiconductor. In contrast, resistivity in the Hall bar geometry saturates to values of about a few resistance quanta. We attribute the metallic-like edge conductance to a nontrivial topology of gapped Dirac spectra.

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Journal Article
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Nature Communications
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20 Feb 2017 13:20
Last Modified:
28 May 2023 03:34