Andreev reflections at metal/superconductor point contacts: Measurement and analysis
Andreev reflections at metal/superconductor point contacts: Measurement and analysis
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DOI：
10.1103/physrevb.63.104510
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发表时间：
2001-02
影响因子：
3.7
通讯作者：
G. Strijkers;Yi Ji;Fengyuan Yang;C. Chien;J. Byers
中科院分区：
文献类型：
--
作者：
G. Strijkers;Yi Ji;Fengyuan Yang;C. Chien;J. Byers
我们提出了X/N B接触的点接触Andreev反射测量，其中X= Ni，Co，Fe和Cu。用Blonder-Tinkham-Klapwijk理论[Phys. Rev. B 25，4515（1982）]分析实验电导-电压曲线，扩展到包括金属的极化P和邻近效应。对于Ni、Co和Fe，电导-电压曲线可以用P和Z作为拟合参数的模型很好地描述，其中Z是模型中包含的无量纲势垒强度，用于描述非理想金属/超导体界面处的弹性散射。Fe、Co和Ni的极化取决于Z的大小。本征P的值可以通过外推到Z= 0（完全透明的界面）来获得。对于Cu，电导-电压曲线示出在Nb超导间隙的位置处的下降，由于邻近效应，这降低了Cu/Nb界面处的正常到超导电流转换的有效间隙值，同时使准粒子传输的差距基本上不变。此外，观察到的差距的整体减少时，点接触的大小接近超导相干长度在Nb。我们已经包括在我们的模型中的这些影响，并获得了很好的协议之间的实验数据和模型计算。
We present point-contact Andreev reflection measurements of X/N b contacts, where X= Ni, Co, Fe, and Cu. Experimental conductance-voltage curves were analyzed with the Blonder-Tinkham-Klapwijk theory [Phys. Rev. B 25, 4515 (1982)], extended to include the polarization P of the metal and proximity effects. For Ni, Co, and Fe the conductance-voltage curves can be well described by the model with P and Z as the fitting parameters, where Z is a dimensionless barrier strength included in the model to describe elastic scattering at a nonideal metal/superconductor interface. The polarization for Fe, Co, and Ni depends on the magnitude of Z. The value of the intrinsic P can be obtained by extrapolation to Z= 0 (perfectly transparent interface). For Cu, the conductance-voltage curves show a dip at the position of the Nb superconducting gap, due to proximity effects, which reduce the effective gap value for the normal to supercurrent conversion at the Cu/Nb interface, while leaving the gap for quasiparticle transport essentially unchanged. In addition, an overall decrease of the gap is observed when the size of the point contact approaches the superconducting coherence length in Nb. We have included these effects in our model and obtained very good agreement between experimental data and model calculations.