The ability to detect and distinguish quantum interference signatures is important for both fundamental research and for the realization of devices such as electron resonators1, interferometers2 and interference-based spin filters3. Consistent with the principles of subwavelength optics, the wave nature of electrons can give rise to various types of interference effects4, such as Fabry–Pérot resonances5, Fano resonances6 and the Aharonov–Bohm effect7. Quantum interference conductance oscillations8 have, indeed, been predicted for multiwall carbon nanotube shuttles and telescopes, and arise from atomic-scale displacements between the inner and outer tubes9,10. Previous theoretical work on graphene bilayers indicates that these systems may display similar interference features as a function of the relative position of the two sheets11,12. Experimental verification is, however, still lacking. Graphene nanoconstrictions represent an ideal model system to study quantum transport phenomena13,14,15 due to the electronic coherence16 and the transverse confinement of the carriers17. Here, we demonstrate the fabrication of bowtie-shaped nanoconstrictions with mechanically controlled break junctions made from a single layer of graphene. Their electrical conductance displays pronounced oscillations at room temperature, with amplitudes that modulate over an order of magnitude as a function of subnanometre displacements. Surprisingly, the oscillations exhibit a period larger than the graphene lattice constant. Charge-transport calculations show that the periodicity originates from a combination of the quantum interference and lattice commensuration effects of two graphene layers that slide across each other. Our results provide direct experimental observation of a Fabry–Pérot-like interference of electron waves that are partially reflected and/or transmitted at the edges of the graphene bilayer overlap region.
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The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.
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S.C. acknowledges a Marie Skłodowska-Curie Individual Fellowship under grant BioGraphING (ID 798851) and P.G. acknowledges a Marie Skłodowska-Curie Individual Fellowship under grant TherSpinMol (ID 748642) from the European Union’s Horizon 2020 research and innovation programme. This work was supported by the Graphene Flagship (a European Union’s Horizon 2020 research and innovation programme under grant agreement no. 649953), the Marie Curie ITN MOLESCO and an ERC advanced grant (Mols@Mols No. 240299). The research by V.M.G.-S., A.G-F. and J.F. was funded by the project FIS2015-63918-R from the Spanish government.