Signatures of valence fluctuations in CeCu2Si2 under high pressure -: art. no. 024508
Signatures of valence fluctuations in CeCu2Si2 under high pressure -: art. no. 024508
复制标题
DOI：
10.1103/physrevb.69.024508
复制
发表时间：
2004-01-01
影响因子：
3.7
通讯作者：
Miyake, K
中科院分区：
文献类型：
--
作者：
Holmes, AT;Jaccard, D;Miyake, K
同时电阻率和交流比热测量已在单晶CeCu_2Si_2上进行压力下超过6 GPa的流体静力学氦压力介质。在超导临界温度Tc（max）的最大值附近，观察到一系列的异常。这些反常现象可能与Ce原子价的突变有关，并表明在压力P（v）等于或等于4.5GPa时存在第二个量子临界点，与环境压力下的自旋涨落相反，临界原子价涨落提供了超导配对机制。这种价态不稳定性和相关的超导性是由一个扩展的安德森晶格模型与库仑排斥之间的传导和f电子预测。我们解释了这幅图中在P-v处发现的T线性电阻率，而在P-v附近发现的其他异常可以使用相同的模型定性地理解。
Simultaneous resistivity and ac specific heat measurements have been performed under pressure on single-crystalline CeCu2Si2 to over 6 GPa in a hydrostatic helium pressure medium. A series of anomalies was observed around the pressure coinciding with a maximum in the superconducting critical temperature, T-c(max). These anomalies can be linked with an abrupt change of the Ce valence and suggest a second quantum critical point at a pressure P(v)similar or equal to4.5 GPa, where critical valence fluctuations provide the superconducting pairing mechanism, as opposed to spin fluctuations at ambient pressure. Such a valence instability-and associated superconductivity-is predicted by an extended Anderson lattice model with Coulomb repulsion between the conduction and f electrons. We explain the T-linear resistivity found at P-v in this picture, while other anomalies found around P-v can be qualitatively understood using the same model.