Temperature dependence of critical current fluctuations in Nb/AlOx/Nb Josephson junctions

Pottorf, Shawn; Patel, Vijay; Lukens, James E.
January 2009
Applied Physics Letters;1/26/2009, Vol. 94 Issue 4, pN.PAG
Academic Journal
We measured the low frequency critical current noise in Nb/AlOx/Nb Josephson junctions. Unshunted junctions biased above the gap voltage and resistively shunted junctions biased near the critical current Ic have been measured. For both, the spectral density of δIc/Ic, Sic(f), is proportional to 1/f, scales inversely as the area A and is independent of Jc≡Ic/A over a factor of nearly 20 in Jc. For all devices measured at 4.2 K, Sic(1 Hz)=2.0±0.4×10-12/Hz when scaled to A=1 μm2. We find that, from 4.2 to 0.46 K, Sic(f) decreases linearly with temperature.


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