arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0902.1009cond-mat.supr-concond-mat.str-el
收藏

重费米子超导体中的Andreev反射和序参量对称性:CeCoIn $_5$的情况

Andreev reflection and order parameter symmetry in heavy-fermion superconductors: the case of CeCoIn$_5$

Wan Kyu Park, Laura H. Greene

摘要:

本文综述了Andreev反射光谱在重费米子研究中的应用现状,重点介绍了临界温度为2.3 K的重费米子超导体CeCoIn $_5$。这是一个完善的技术,研究超导序参量通过测量的微分电导从纳米金属结。Andreev反射在CeCoIn $_5$中清楚地观察到,在其他重费米子超导体。与理论预测值(100%)相比,测量的Andreev信号高度降低到最大值$\sim$ 13%的量级。利用扩展的BTK模型对电导谱进行分析,定性地测量了CeCoIn $_5$中的超导序参量对称性,确定其为$d_{x^2-y^2}$波.提出了一个唯象模型,采用两个电导通道之间的Fano干涉效应,以解释电导不对称性和减少Andreev信号。这个模型似乎是合理的,不仅因为它提供了良好的拟合数据,但也因为它是非常有可能的,通过两个通道,一个进入重电子液体和其他进入传导电子连续发生的电传导。进一步的实验和理论研究将揭示相干重电子液体如何从近藤晶格(一个典型的强关联电子系统)中出现的机制。还讨论了未解决的问题和未来的发展方向。

英文摘要:

We review the current status of Andreev reflection spectroscopy on the heavy fermions, mostly focusing on the case of CeCoIn$_5$, a heavy-fermion superconductor with a critical temperature of 2.3 K. This is a well-established technique to investigate superconducting order parameters via measurements of the differential conductance from nanoscale metallic junctions. Andreev reflection is clearly observed in CeCoIn$_5$ as in other heavy-fermion superconductors. The measured Andreev signal is highly reduced to the order of maximum $\sim$ 13% compared to the theoretically predicted value (100%). Analysis of the conductance spectra using the extended BTK model provides a qualitative measure for the superconducting order parameter symmetry, which is determined to be $d_{x^2-y^2}$-wave in CeCoIn$_5$. A phenomenological model is proposed employing a Fano interference effect between two conductance channels in order to explain both the conductance asymmetry and the reduced Andreev signal. This model appears plausible not only because it provides good fits to the data but also because it is highly likely that the electrical conduction occurs via two channels, one into the heavy electron liquid and the other into the conduction electron continuum. Further experimental and theoretical investigations will shed new light on the mechanism of how the coherent heavy-electron liquid emerges out of the Kondo lattice, a prototypical strongly correlated electron system. Unresolved issues and future directions are also discussed.

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。

↑