Meta-Orbital Transition in Heavy-Fermion Systems: Analysis by Dynamical Mean Field Theory and Self-Consistent Renormalization Theory of Orbital Fluctuations
Meta-Orbital Transition in Heavy-Fermion Systems: Analysis by Dynamical Mean Field Theory and Self-Consistent Renormalization Theory of Orbital Fluctuations
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DOI：
10.1143/jpsj.79.114717
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发表时间：
2010-11-01
影响因子：
1.7
通讯作者：
Hattori, Kazumasa
中科院分区：
文献类型：
--
作者：
Hattori, Kazumasa
基于动态平均场理论和静态平均场近似，研究了具有Ising轨道交换作用的双轨道安德森晶格模型.针对铈基重费米子化合物，我们研究了两个轨道状态之间的轨道交叉，当每个站点的总f-电子数n（f）接近1。我们表明，“亚轨道”的过渡，在这两个轨道的占有率急剧变化，发生在基态的f-电子轨道和传导电子之间的杂化小于激发的f-电子轨道和传导电子在低压下。在亚轨道临界端点附近，轨道涨落增强，并与电荷涨落耦合。将巡游电子磁性的自洽重整化理论应用于轨道涨落，发展了亚轨道涨落的临界理论。临界终点，一阶过渡，和交叉内描述的轨道波动的高斯近似。我们讨论了我们的研究结果的相关性CeAl 2，CeCu 2Si 2，CeCu 2Ge 2，和相关的化合物，这都有低的晶体电场激发态。
We investigate a two-orbital Anderson lattice model with Ising orbital intersite exchange interactions on the basis of a dynamical mean field theory combined with the static mean field approximation of intersite orbital interactions. Focusing on Ce-based heavy-fermion compounds, we examine the orbital crossover between two orbital states, when the total f-electron number per site n(f) is similar to 1. We show that a "meta-orbital" transition, at which the occupancy of two orbitals changes steeply, occurs when the hybridization between the ground-state f-electron orbital and conduction electrons is smaller than that between the excited f-electron orbital and conduction electrons at low pressures. Near the meta-orbital critical end point, orbital fluctuations are enhanced and couple with charge fluctuations. A critical theory of meta-orbital fluctuations is also developed by applying the self-consistent renormalization theory of itinerant electron magnetism to orbital fluctuations. The critical end point, first-order transition, and crossover are described within Gaussian approximations of orbital fluctuations. We discuss the relevance of our results to CeAl2, CeCu2Si2, CeCu2Ge2, and related compounds, which all have low-lying crystalline-electric-field excited states.