Investigation of Supercurrent in the Quantum Hall Regime in Graphene Josephson Junctions
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In this study, we examine multiple encapsulated graphene Josephson junctions to determine which mechanisms may be responsible for the supercurrent observed in the quantum Hall (QH) regime. Rectangular junctions with various widths and lengths were studied to identify which parameters affect the occurrence of QH supercurrent. We also studied additional samples where the graphene region is extended beyond the contacts on one side, making that edge of the mesa significantly longer than the opposite edge. This is done in order to distinguish two potential mechanisms: (a) supercurrents independently flowing along both non-contacted edges of graphene mesa, and (b) opposite sides of the mesa being coupled by hybrid electron–hole modes flowing along the superconductor/graphene boundary. The supercurrent appears suppressed in extended junctions, suggesting the latter mechanism.
KeywordsGraphene Supercurrent Josephson junction Quantum Hall
Low-temperature electronic measurements performed by A.W.D., M.T.W., C.T.K., and G.F. were supported by ARO Award W911NF-16-1-0122. Sample fabrication and characterization conducted by M.T.W., A.S., C.T.K., and G.F. were supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy, under Award DE-SC0002765. F.A. acknowledges the ARO under Award W911NF-16-1-0132. I.V.B. and M.Y. acknowledge the Canon foundation. This work was performed in part at the Duke University Shared Materials Instrumentation Facility (SMIF), a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), which is supported by the National Science Foundation (Grant ECCS-1542015) as part of the National Nanotechnology Coordinated Infrastructure (NNCI). M. Y. acknowledges support from JSPS KAKENHI Grant No. JP25107003. K. W. and T. T. acknowledge support from JSPS KAKENHI Grant No. JP15K21722 and the Elemental Strategy Initiative conducted by the MEXT, Japan. T. T. acknowledges support from JSPS Grant-in-Aid for Scientific Research A (No. 26248061) and JSPS Innovative Areas ‘Nano Informatics’ (No. 25106006). M. Y. and S. T. acknowledge support by Grant-in-Aid for Scientific Research S (No. 26220710), and Grant-in-Aid for Scientific Research A (Nos. 26247050, 16H02204).