Critical current fluctuations in graphene Josephson junctions
Authors: Mohammad T. Haque, MarcoWill, MattiTomi, Preeti Pandey, Manohar Kumar, Felix Schmidt, Kenji Watanabe, TakashiTaniguchi, Romain Danneau, Gary Steele and Pertti Hakonen
Scientific Reports volume 11, Article number: 19900 (2021)
Abstract: We have studied 1/f noise in critical current IcIc 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≃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 vrfvrf at 600–650 MHz. We find 1/f critical current fluctuations on the order of δIc/Ic≃10−3δIc/Ic≃10−3 per unit band at 1 Hz. The noise power spectrum of critical current fluctuations SIcSIc measured near the Dirac point at large, sub-critical rf-carrier amplitudes obeys the law SIc/Ic2=a/fβSIc/Ic2=a/fβ where a≃4×10−6a≃4×10−6 and β≃1β≃1 at f>0.1f>0.1 Hz. Our results point towards significant fluctuations in IcIc originating from variation of the proximity induced gap in the graphene junction.