Haque Mohammad T, Will Marco, Tomi Matti, Pandey Preeti, Kumar Manohar, Schmidt Felix, Watanabe Kenji, Taniguchi Takashi, Danneau Romain, Steele Gary, Hakonen Pertti
Low Temperature Laboratory, QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, 00076, Aalto, Finland.
Kavli Institute of NanoScience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft, The Netherlands.
Sci Rep. 2021 Oct 6;11(1):19900. doi: 10.1038/s41598-021-99398-3.
We have studied 1/f noise in critical current [Formula: see text] 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 [Formula: see text] nA. The low frequency noise in the superconducting state is measured by tracking the variation in magnitude and phase of a reflection carrier signal [Formula: see text] at 600-650 MHz. We find 1/f critical current fluctuations on the order of [Formula: see text] per unit band at 1 Hz. The noise power spectrum of critical current fluctuations [Formula: see text] measured near the Dirac point at large, sub-critical rf-carrier amplitudes obeys the law [Formula: see text] where [Formula: see text] and [Formula: see text] at [Formula: see text] Hz. Our results point towards significant fluctuations in [Formula: see text] originating from variation of the proximity induced gap in the graphene junction.
我们研究了由NbTiN电极接触的h-BN封装单层石墨烯中临界电流(I_c)的1/f噪声。该样品接近扩散极限，在狄拉克点处具有滞后现象的开关超电流达到(I_{c0}) nA。通过跟踪600 - 650 MHz下反射载波信号(S_{11})的幅度和相位变化来测量超导状态下的低频噪声。我们发现在1 Hz时，每单位能带的1/f临界电流波动量级为(I_{c0})。在大的亚临界射频载波幅度下，在狄拉克点附近测量的临界电流波动(S_{I_c I_c})的噪声功率谱遵循规律(S_{I_c I_c}(f)=S_{I_c I_c}(f_0)(f/f_0)^{-\alpha})，其中(\alpha)在(f_0) = 1 Hz时为(\alpha)，且(S_{I_c I_c}(f_0))为(S_{I_c I_c}(f_0))。我们的结果表明，由于石墨烯结中近邻诱导能隙的变化，(I_c)存在显著波动。
