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arXiv 1809.09510cond-mat.supr-con
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纳米桥超导量子干涉器件:超越约瑟夫森极限

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

Dibyendu Hazra

摘要:

纳米级超导量子干涉器件(纳米SQUIDS),其中弱连接由纳米桥制成-即,纳米桥-SQUID(NBSs)-是纳米尺度磁力测量中最灵敏的磁力计之一。由于纳米桥-电极接头中非常强的非线性,NBS的所施加的磁通量($Φ_{a}$)-临界电流($I_{c}$)特性与常规隧道结SQUID非常显著地不同,尤其是当纳米桥长和/或屏蔽参数大时。然而,在大多数的理论描述中,NBSs被视为传统的隧道结SQUID,这是基于直流约瑟夫森效应。在这里,我提出了一个模型表明,对于长的纳米桥和/或大的屏蔽参数的$I_{c}(Φ_{a})$的NBS可以解释仅考虑磁通量子化的NBS环路和能量的NBS,它是没有必要考虑约瑟夫森效应。我还证明,使用该模型,我们可以得到有用的表达式,如调制深度和传递函数。我还讨论了动力学电感分数($κ$)在确定$I_{c}(Φ_{a})$中的作用。

英文摘要:

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 ($Φ_{a}$) -- 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 $I_{c}(Φ_{a})$ 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 ($κ$) in determining $I_{c}(Φ_{a})$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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