Edge currents shunt the insulating bulk in gapped graphene

M. J. Zhu, A. V. Kretinin, M. D. Thompson, D. A. Bandurin, S. Hu, G. L. Yu, J. Birkbeck, A. Mishchenko, I. J. Vera-Marun, K. Watanabe, T. Taniguchi, M. Polini, J. R. Prance, K. S. Novoselov, A. K. Geim () and M. Ben Shalom ()
Additional contact information
M. J. Zhu: School of Physics and Astronomy, The University of Manchester
A. V. Kretinin: National Graphene Institute, The University of Manchester
M. D. Thompson: University of Lancaster
D. A. Bandurin: School of Physics and Astronomy, The University of Manchester
S. Hu: School of Physics and Astronomy, The University of Manchester
G. L. Yu: School of Physics and Astronomy, The University of Manchester
J. Birkbeck: School of Physics and Astronomy, The University of Manchester
A. Mishchenko: School of Physics and Astronomy, The University of Manchester
I. J. Vera-Marun: School of Physics and Astronomy, The University of Manchester
K. Watanabe: National Institute for Materials Science
T. Taniguchi: National Institute for Materials Science
M. Polini: Istituto Italiano di Tecnologia, Graphene Labs
J. R. Prance: University of Lancaster
K. S. Novoselov: School of Physics and Astronomy, The University of Manchester
A. K. Geim: School of Physics and Astronomy, The University of Manchester
M. Ben Shalom: School of Physics and Astronomy, The University of Manchester

Nature Communications, 2017, vol. 8, issue 1, 1-6

Abstract: Abstract 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.

Date: 2017
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DOI: 10.1038/ncomms14552

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