High Efficiency CVD Graphene-lead (Pb) Cooper Pair Splitter
Craciun, Monica F.
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We demonstrate high efficiency Cooper pair splitting in a graphene-based device. We utilize a true Y-shape design effectively placing the splitting channels closer together: graphene is used as the central superconducting electrode as well as QD output channels, unlike previous designs where a conventional superconductor was used with tunnel barriers to the quantum dots (QD) of a different material. Superconductivity in graphene is induced via the proximity effect, thus resulting in both a large measured superconducting gap $\Delta=0.5$meV, and a long coherence length $\xi=200$nm. The graphene-graphene, flat, two dimensional, superconductor-QD interface lowers the capacitance of the quantum dots, thus increasing the charging energy $E_C$ (in contrast to previous devices). As a result we measure a visibility of up to 96% and a splitting efficiency of up to 62%. Finally, the devices utilize graphene grown by chemical vapor deposition allowing for a standardized device design with potential for increased complexity.
I. V. B. acknowledges the JSPS International Research Fellowship. M. Y. and S. T. acknowledge financial support by Grant-in-Aid for Scientific Research S (No. 26220710) and Grant-in-Aid for Scientific Research A (No. 26247050). M. Y. acknowledges financial support by Grant-in-Aid for Scientific Research on Innovative Areas ”Science of Atomic Layers” and Canon foundation. S. T. acknowledges financial support by MEXT project for Developing Innovation Systems and JST Strategic International Cooperative Program. S. R. and M. F. C. acknowledge financial support from EPSRC (Grant EP/J000396/1, EP/K017160, EP/K010050/1, EP/G036101/1, EP/M002438/1, EP/M001024/1), from the Royal Society Travel Exchange Grants 2012 and 2013 and from the Leverhulme Trust.
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Scientific Reports 6, Article number: 23051