Critical current fluctuations in graphene Josephson junctions
Mohammad T. Haque (Aalto University)
Marco Will (Aalto University)
Matti Tomi (Aalto University)
Preeti Pandey (Aalto University)
Manohar Kumar (Aalto University)
Felix Schmidt (Kavli institute of nanoscience Delft, TU Delft - Applied Sciences)
Kenji Watanabe (National Institute for Materials Science)
Takashi Taniguchi (National Institute for Materials Science)
Gary Steele (TU Delft - Applied Sciences, Kavli institute of nanoscience Delft)
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Abstract
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.
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