Critical current fluctuations in graphene Josephson junctions

We have studied 1/f noise in critical current I c 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 similar or equal 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 v(rf) at 600-650 MHz. We find 1/f critical current fluctuations on the order of delta I-c/I-c similar or equal to 10(-3) per unit band at 1 Hz. The noise power spectrum of critical current fluctuations S Ic measured near the Dirac point at large, sub-critical rf-carrier amplitudes obeys the law S-Ic/I-c2 = alpha/f(beta) where alpha similar or equal to 4 x 10(-6) and beta similar or equal to 1 at f > 0.1 Hz. Our results point towards significant fluctuations in I-c originating from variation of the proximity induced gap in the graphene junction.

Automated summary

The study focused on 1/f noise in critical current Ic in h-BN encapsulated monolayer graphene contacted by NbTiN electrodes, finding fluctuations on the order of 10^(-3) and obeying a power law in the noise power spectrum. The results suggest significant fluctuations in Ic arising from variation of the proximity induced gap in the graphene junction.