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arXiv 0712.3241cond-mat.supr-concond-mat.str-el
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非均匀超导导线的电阻率

Resistivity of Inhomogeneous Superconducting Wires

G. Venketeswara Pai, E. Shimshoni, N. Andrei

摘要:

本文研究了超导序参量中的量子相位涨落对不均匀超导导线低温电阻率$ρ(T)$的贡献。特别是,我们占任意大小的线厚度的随机空间波动。对于超导体-绝缘体转变临界值以上的典型导线厚度,相位滑移过程可以微扰处理。我们使用的记忆形式主义的方法,它强调了弱违反守恒定律的机制中产生有限电阻率所发挥的作用。我们的计算产生一个表达式为$ρ(T)$,它表现出一个平滑的交叉从均匀的“颗粒”的限制后,增加$T$,控制的“粒度参数”$D$的厚度波动的大小的特点。对于极小的$D$,我们恢复了由量子相移解束缚得到的幂律依赖性$ρ(T)\sim T^α$.然而,在强非齐次极限下,指数$α$被修改,前因子是{ \em指数增强}。我们研究的指数$α$上的外部磁场施加平行于导线的依赖性。最后,我们表明,在低$T$的幂律依赖性是一致的,在各种长而窄的样品中获得的一系列实验数据。从数据中提取的$α$值以及相应的场依赖性与相应样品的已知参数一致。

英文摘要:

We study the contribution of quantum phase fluctuations in the superconducting order parameter to the low--temperature resistivity $ρ(T)$ of a dirty and inhomogeneous superconducting wire. In particular, we account for random spatial fluctuations of arbitrary size in the wire thickness. For a typical wire thickness above the critical value for superconductor--insulator transition, phase--slips processes can be treated perturbatively. We use a memory formalism approach, which underlines the role played by weak violation of conservation laws in the mechanism for generating finite resistivity. Our calculations yield an expression for $ρ(T)$ which exhibits a smooth crossover from a homogeneous to a ``granular'' limit upon increase of $T$, controlled by a ``granularity parameter'' $D$ characterizing the size of thickness fluctuations. For extremely small $D$, we recover the power--law dependence $ρ(T)\sim T^α$ obtained by unbinding of quantum phase--slips. However in the strongly inhomogeneous limit, the exponent $α$ is modified and the prefactor is {\em exponentially enhanced}. We examine the dependence of the exponent $α$ on an external magnetic field applied parallel to the wire. Finally, we show that the power--law dependence at low $T$ is consistent with a series of experimental data obtained in a variety of long and narrow samples. The values of $α$ extracted from the data, and the corresponding field dependence, are consistent with known parameters of the corresponding samples.

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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