From Kondo Lattices to Kondo Superlattices
From Kondo Lattices to Kondo Superlattices
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从近藤晶格到近藤超晶格
DOI：
10.1088/0034-4885/79/7/074503
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Y. Matsuda
中科院分区：
文献类型：
--
作者：
M. Shimozawa;S.K. Goh;T. Shibauchi;Y. Matsuda
在强关联电子系统中实现新的基态仍然是凝聚态物理中的一个主要问题。重费米子材料的电子结构基本上是三维的，由于其与多体效应相关的有趣特性，是获得新电子态的最合适的系统之一。最近，发展了一种最先进的分子束外延技术，通过制造包含重费米子化合物的人工超晶格来降低重电子系统的维数;这种方法可以在二维（2D）重费米子系统中产生一种新型的电子态。在反铁磁性重费米子化合物CeIn 3和常规金属LaIn 3的人工超晶格中，通过减小CeIn 3层的厚度来抑制磁有序。此外，重费米子的二维限制导致有效电子质量的增强和偏离标准费米液体的电子性质，这两者都与量子临界的维度调谐有关。在重费米子超导体CeCoIn 5和重金属YbCoIn 5的超导超晶格中，即使在CeCoIn 5的一个晶胞层的厚度下也观察到超导性的特征。这种2D重费米子超导体的最显着特征是CeCoIn 5层的厚度减小显著改变了上临界场的温度和角度依赖性。这一结果归因于通过CeCoIn 5块层界面处的局部反转对称破缺对Pauli对破缺效应的实质性抑制。该系统中的反转对称性破缺的重要性也得到了位点选择性核磁共振光谱的支持，该光谱可以单独解析来自每个层的光谱信息，即使在相同的CeCoIn 5块层内。此外，最近涉及CeCoIn 5/YbCoIn 5超晶格的实验表明，反转对称性破缺的程度，反过来，Rashba分裂是可控的，提供了实现更迷人的超导态的前景。因此，这些近藤超晶格为探索非常规金属和超导态铺平了道路。
The realization of new classes of ground states in strongly correlated electron systems continues to be a major issue in condensed matter physics. Heavy fermion materials, whose electronic structure is essentially three-dimensional, are one of the most suitable systems for obtaining novel electronic states because of their intriguing properties associated with many-body effects. Recently, a state-of-the-art molecular beam epitaxy technique was developed to reduce the dimensionality of heavy electron systems by fabricating artificial superlattices that include heavy fermion compounds; this approach can produce a new type of electronic state in two-dimensional (2D) heavy fermion systems. In artificial superlattices of the antiferromagnetic heavy fermion compound CeIn 3 and the conventional metal LaIn 3, the magnetic order is suppressed by a reduction in the thickness of the CeIn 3 layers. In addition, the 2D confinement of heavy fermions leads to enhancement of the effective electron mass and deviation from the standard Fermi liquid electronic properties, which are both associated with the dimensional tuning of quantum criticality. In the superconducting superlattices of the heavy fermion superconductor CeCoIn 5 and nonmagnetic metal YbCoIn 5, signatures of superconductivity are observed even at the thickness of one unit-cell layer of CeCoIn 5. The most remarkable feature of this 2D heavy fermion superconductor is that the thickness reduction of the CeCoIn 5 layers changes the temperature and angular dependencies of the upper critical field significantly. This result is attributed to a substantial suppression of the Pauli pair-breaking effect through the local inversion symmetry breaking at the interfaces of CeCoIn 5 block layers. The importance of the inversion symmetry breaking in this system has also been supported by site-selective nuclear magnetic resonance spectroscopy, which can resolve spectroscopic information from each layer separately, even within the same CeCoIn 5 block layer. In addition, recent experiments involving CeCoIn 5/YbCoIn 5 superlattices have shown that the degree of the inversion symmetry breaking and, in turn, the Rashba splitting are controllable, offering the prospect of achieving even more fascinating superconducting states. Thus, these Kondo superlattices pave the way for the exploration of unconventional metallic and superconducting states.