期刊
JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN
卷 79, 期 11, 页码 -出版社
PHYSICAL SOC JAPAN
DOI: 10.1143/JPSJ.79.114717
关键词
dynamical mean field theory; two-orbital Anderson lattice model; self-consistent renormalization theory; critical end point; orbital fluctuations
资金
- Japan Society for the Promotion of Science [20740189]
- Grants-in-Aid for Scientific Research [20740189] Funding Source: KAKEN
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.
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