Temperature Dependence of Critical Current Fluctuations in Nb/AlO${}_{\mathrm{x}}$/Nb Josephson Junctions

Abstract

We have measured the low frequency critical current noise in Nb/AlO${}_{\mathrm{x}}$/Nb Josephson junctions. Unshunted junctions biased above the gap voltage and resistively shunted junctions biased near the critical current, $I_c$, have been measured. For both, the spectral density of $\delta I_c/I_c$, $S_{i_c}(f)$, is proportional to $1/f$, scales inversely as the area, $A$, and is independent of $J_c\equiv I_c/A$ over a factor of nearly 20 in $J_c$. For all devices measured at 4.2 K, $S_{i_c}$(1 Hz)$=2.0\pm 0.4\cdot 10^{-12}$/Hz when scaled to A=1 $\mu$m${}^2$. We find that, from 4.2 K to 0.46 K, $S_{i_c}(f)$ decreases linearly with temperature.

References in corpus (2)

• Low-frequency Noise in Josephson Junctions for Superconducting Qubits
• Microscopic Model of Critical Current Noise in Josephson Junctions