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arXiv 0908.1384cond-mat.supr-con
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具有带间耦合的弹道$s_\pm$波超导体中的量子输运:电导谱、约瑟夫森电流和交叉Andreev反射

Quantum transport in ballistic $s_\pm$-wave superconductors with interband coupling: conductance spectra, Josephson current, and crossed Andreev reflection

Iver Bakken Sperstad, Jacob Linder, Asle Sudbø

摘要:

我们研究了弹道$s_\pm$波超导体中的量子输运,其中包括两个带之间的耦合,并将我们的模型应用于三种可能的探针,用于检测这种配对状态的内部相移:N $|s_\pm$波结中的隧道光谱,双引线N $|s_\pm$波$|$ N系统中的交叉Andreev反射,和S波$|$/$|s_\pm$波约瑟夫森结中的约瑟夫森电流。而前两个探针是不敏感的超导相在没有带间耦合,约瑟夫森效应本质上是相位相关的,而且被证明是相对不敏感的带间耦合的强度。聚焦于约瑟夫森电流,我们发现0- $π$跃迁作为两个带的有效势垒透明度的比率的函数,以及作为温度的函数的类似的相移效应。这个$s_\pm$波模型的一个基本特征是非正弦性的电流相位关系,我们计算的依赖性的临界电流上的外部磁场,显示如何这个功能可能是实验观察到的这个系统。我们还评论了可能的实验检测的相移效应在$s_\pm$波超导体。

英文摘要:

We study quantum transport in ballistic $s_\pm$-wave superconductors where coupling between the two bands is included, and apply our model to three possible probes for detecting the internal phase shift of such a pairing state: tunneling spectroscopy in a N$|s_\pm$-wave junction, crossed Andreev reflection in a two-lead N$|s_\pm$-wave$|$N system, and Josephson current in a s-wave$|$I$|s_\pm$-wave Josephson junction. Whereas the first two probes are insensitive to the superconducting phase in the absence of interband coupling, the Josephson effect is intrinsically phase-dependent, and is moreover shown to be relatively insensitive to the strength of the interband coupling. Focusing on the Josephson current, we find a 0-$π$ transition as a function of the ratio of effective barrier transparency for the two bands, as well as a similar phase-shift effect as a function of temperature. An essential feature of this $s_\pm$-wave model is non-sinusoidality of the current-phase relation, and we compute the dependence of the critical current on an external magnetic field, showing how this feature may be experimentally observable for this system. We also comment on the possible experimental detection of the phase shift effects in $s_\pm$-wave superconductors.

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