Nano-bridge Superconducting Quantum Interference Devices: beyond the Josephson limit

Abstract

Nano-scale superconducting quantum interference devices (nano-SQUIDS) where the weak-links are made from nano-bridges --- i.e., nano-bridge--SQUIDs (NBSs) --- are one of the most sensitive magnetometers for nano-scale magnetometry. Because of very strong non-linearity in the nano-bridge--electrode joints, the applied magnetic flux (${\Phi }_a$) -- critical current ($I_c$) characteristics of NBSs differ very significantly from conventional tunnel-junction-SQUIDs, especially when nano-bridges are long and/or the screening parameter is large. However, in most of the theoretical descriptions, NBSs have been treated like conventional tunnel-junction-SQUIDs, which are based on d.c. Josephson effect. Here, I present a model demonstrating that for long nano-bridges and/or large screening parameter the $I_c({\Phi }_a)$ of a NBS can be explained by merely considering the fluxoid quantization in the NBS loop and the energy of the NBS; it is not necessary to take the Josephson effect into consideration. I also demonstrate that using the model, we can derive useful expressions like modulation depth and transfer function. I also discuss the role of kinetic inductance fraction ($\kappa$) in determining $I_c({\Phi }_a)$.

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Cited by in corpus (4)

• The impact of kinetic inductance on the critical current oscillations of nanobridge SQUIDs
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• Nonvolatile Cryogenic Phase Slip Memory with Single-Shot Readout
• Improving spatial resolution of scanning SQUID microscopy with an on-chip design