Standard measurement method for normal state resistance and critical current of resistively shunted Josephson junctions
Standard measurement method for normal state resistance and critical current of resistively shunted Josephson junctions
复制标题
电阻分流约瑟夫森结正常状态电阻和临界电流的标准测量方法
DOI：
10.1088/1361-6668/ac4f3b
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发表时间：
2022
影响因子：
3.6
通讯作者：
C P Foley and R L Fagaly
中科院分区：
文献类型：
--
作者：
M Ohkubo;G Uehara;J Beyer;M Mimura;H Tanaka;K Ehara;S Tanaka;T Noguchi;E E Mitchell;C P Foley and R L Fagaly
约瑟夫森结的一个重要参数是正常态电阻(Rn)和临界电流(Ic)的乘积，用于设计超导模拟器件或数字电路。从电压-电流(U-I)特性曲线确定Rn和Ic常常面临困难；特别是Ic会被内部热噪声或外部电噪声大大降低。本文提出了液氮中高温超导体晶界Jj和液氦中低T超导体多层superconductor/normal-conductor/superconductor(SnS)Jj的Rn和本征临界电流的标准测量方法。该方法的适用条件是高温超导和低温超导JJ都具有与电阻分流结(RSJ)模型相容的U-I曲线。采用几何均值准则和最小二乘拟合法结合RSJ模型提取Rn和Ici值，消除了噪声舍入和自热对U-I曲线的两种失真影响。当用户遵循标准协议时，组合方法可确保Rn的相对标准不确定度为1.9%，Ici或更好的相对标准不确定度为8%。结果表明，对于77K附近的d波高温超导JJ和具有较大结参数范围的S波高温超导JJ，无论d波超导体在较低温度下发生0-π结相变等特性，组合方法都是有效的。这项工作是促进JJS超导电子学标准化的第一步。
An important parameter of Josephson junctions (JJs) is the product of normal state resistance (R n) and critical current (I c) for designing superconductor analogue devices or digital circuits. Determination of R n and I c from voltage–current (U–I) characteristic curves often faces difficulties; in particular I c is considerably reduced by intrinsic thermal or extrinsic electrical noises. Here, we propose a standard measurement method of R n and intrinsic critical current (I ci) for high-T c superconductor (HTS) grain boundary JJs operated in liquid nitrogen and low-T c superconductor (LTS) multilayer superconductor/normal-conductor/superconductor (SNS) JJs in liquid helium. The applicable condition of this method is that both HTS and LTS JJs have U–I curves compatible with resistively-shunted junction (RSJ) model. Both R n and I ci values are extracted by combining a geometric mean criterion to select a data set and a least-squares fitting method with the RSJ model, eliminating two distortion effects on U–I curves: noise-rounding and self-heating. The combined method ensures relative standard uncertainty values of 1.9% for R n and 8% for I ci or better, when the users follow the standard protocol. It is demonstrated that the combined method is valid for d-wave HTS JJs near 77 K, regardless of peculiarities such as 0–π junction transition in d-wave superconductors at lower temperatures, and s-wave LTS SNS JJs with a wide range of junction parameters. This work is the first step to facilitate standardization for superconductor electronics with JJs.