Temperature-Independent Fermi Surface in the Kondo Lattice YbRh2Si2
Temperature-Independent Fermi Surface in the Kondo Lattice YbRh2Si2
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DOI：
10.1103/physrevx.5.011028
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发表时间：
2015-03-12
影响因子：
12.5
通讯作者：
Vyalikh, D. V.
中科院分区：
文献类型：
--
作者：
Kummer, K.;Patil, S.;Vyalikh, D. V.
强关联电子系统是当代固体物理的中心课题之一。这种系统的突出例子是近藤晶格，即，金属间化合物材料，其中低于临界温度（近藤温度T-K），磁矩变得淬灭并且传导电子的有效质量接近质子的质量。在Ce和Yb基系统中，这种所谓的重费米子行为是由强定域4f和巡回电子之间的相互作用引起的。在这方面，一个主要的和非常有争议的讨论的问题是如何在费米面（FS）的本地化的电子自由度参与增加两种电子之间的相互作用或改变温度。在本文中，我们表明，FS的原型近藤晶格，YbRh 2Si 2，不改变其大小或形状在很宽的温度范围内延伸远低于远高于单离子近藤温度T-K类似于25 K的这个系统。这个实验观察，通过角度分辨光电子能谱，是在显着的对比，从一个大的FS，包括4f自由度，一个小的FS，没有4f的，温度升高时，广泛认为的演变。我们的结果明确表明，需要进一步推进的理论方法的基础上的周期性安德森模型，以阐明费米面的温度依赖性的近藤晶格。
Strongly correlated electron systems are one of the central topics in contemporary solid-state physics. Prominent examples for such systems are Kondo lattices, i.e., intermetallic materials in which below a critical temperature, the Kondo temperature T-K, the magnetic moments become quenched and the effective masses of the conduction electrons approach the mass of a proton. In Ce-and Yb-based systems, this so-called heavy-fermion behavior is caused by interactions between the strongly localized 4f and itinerant electrons. A major and very controversially discussed issue in this context is how the localized electronic degree of freedom gets involved in the Fermi surface (FS) upon increasing the interaction between both kinds of electrons or upon changing the temperature. In this paper, we show that the FS of a prototypic Kondo lattice, YbRh2Si2, does not change its size or shape in a wide temperature range extending from well below to far above the single-ion Kondo temperature T-K similar to 25 K of this system. This experimental observation, obtained by means of angle-resolved photoemission spectroscopy, is in remarkable contrast to the widely believed evolution from a large FS, including the 4f degrees of freedom, to a small FS, without the 4f's, upon increasing temperature. Our results explicitly demonstrate a need to further advance in theoretical approaches based on the periodic Anderson model in order to elucidate the temperature dependence of Fermi surfaces in Kondo lattices.