Critical current fluctuations in graphene Josephson junctions

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Scientific Reports, Volume 11, issue 1
We have studied 1/f noise in critical current Ic in h-BN encapsulated monolayer graphene contacted by NbTiN electrodes. The sample is close to diffusive limit and the switching supercurrent with hysteresis at Dirac point amounts to ≃ 5 nA. The low frequency noise in the superconducting state is measured by tracking the variation in magnitude and phase of a reflection carrier signal vrf at 600–650 MHz. We find 1/f critical current fluctuations on the order of δIc/ Ic≃ 10 - 3 per unit band at 1 Hz. The noise power spectrum of critical current fluctuations SIc measured near the Dirac point at large, sub-critical rf-carrier amplitudes obeys the law SIc/Ic2=a/fβ where a≃ 4 × 10 - 6 and β≃ 1 at f> 0.1 Hz. Our results point towards significant fluctuations in Ic originating from variation of the proximity induced gap in the graphene junction.
| openaire: EC/H2020/670743/EU//QuDeT | openaire: EC/H2020/722923/EU//OMT | openaire: EC/H2020/785219/EU//GrapheneCore2 Funding Information: We are grateful to Dmitry Golubev, Andreas Hüttel, Alexander Melnikov, and Elisabetta Paladino for discussions. This work was supported by the Academy of Finland projects 314448 (BOLOSE), 310086 (LTnoise) and 336813 (CoE, Quantum Technology Finland) as well as partly by ERC (Grant No. 670743) and COST Action CA16218 (NANOCOHYBRI). This research project utilized the Aalto University OtaNano/LTL infrastructure which is part of European Microkelvin Platform EMP (funded by European Union’s Horizon 2020 Research and Innovation Programme Grant No. 824109). MTH acknowledges support from the European Union’s Horizon 2020 Programme for Research and Innovation under Grant Agreement No. 722923 (Marie Curie ETN - OMT). This work was partly supported by Helmholtz society through program STN and the DFG via the projects DA 1280/3-1. FS and GS acknowledge funding from the European Union Horizon 2020 research and innovation programme under Grant Agreement No. 785219 - GrapheneCore2. KW and TT acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, Grant No. JPMXP0112101001 and JSPS KAKENHI Grant No. JP20H00354. Publisher Copyright: © 2021, The Author(s).
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Haque , M T , Will , M , Tomi , M , Pandey , P , Kumar , M , Schmidt , F , Watanabe , K , Taniguchi , T , Danneau , R , Steele , G & Hakonen , P 2021 , ' Critical current fluctuations in graphene Josephson junctions ' , Scientific Reports , vol. 11 , no. 1 , 19900 .