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arXiv · 1412.3456

Josephson coupling between superconducting islands on single and bilayer graphene

Francesco Mancarella·Jonas Fransson·Alexander Balatsky
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Abstract

We study the Josephson coupling of superconducting (SC) islands through the surface of single-layer (SLG) and bilayer (BLG) graphene, as a function of distance between the grains, temperature, chemical potential and external (transverse) gate-voltage. For SLG, we provide a comparison with existing literature. The proximity effect is analyzed through a Matsubara Green function approach. This represents the first step in a discussion of the conditions for the onset of a granular superconductivity within the film, made possible by Josephson currents flowing between superconductors. To ensure phase coherence over the 2D sample, a random spatial distribution can be assumed for the SC islands on the SLG sheet (or intercalating the BLG sheets). The tunable gate-voltage-induced band gap of BLG affects the asymptotic decay of the Josephson coupling-distance characteristic for each pair of SC islands in the sample, which results in the end in a qualitatively strong field-dependence of the relation between Berezinskii-Kosterlitz-Thouless transition critical temperature and gate-voltage.

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Francesco Mancarella, Jonas Fransson, Alexander Balatsky. 2014-12-10. Josephson coupling between superconducting islands on single and bilayer graphene. https://doi.org/10.1088/0953-2048%2F29%2F5%2F054004

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