paper

Microscopic Theory of Quadrupole Ordering in Pr Compounds on the Basis of a - Coupling Scheme

arXiv:1902.05736 · doi:10.7566/JPSJ.88.034715

Abstract

Toward the understanding of incommensurate quadrupole ordering in PrPb, we develop a microscopic theory of multipole ordering in -electron systems from an itinerant picture on the basis of a - coupling scheme. For this purpose, we introduce the - Hubbard model on a simple cubic lattice with the effective interactions that induce local states. By evaluating multipole susceptibility in a random phase approximation, we find that the hybridization between and orbitals plays a key role in the emergence of quadrupole ordering. We also emphasize that quadrupole ordering can be understood from the concept of {\it multipole nesting}, in which the Fermi surface region with large orbital density should be nested on the area with a significant component when the positions of the Fermi surfaces are shifted by the ordering vector. This concept cab be intuitively understood from the fact that local doublets are mainly composed of two singlets between and orbitals. Finally, we discuss the possible relevance of the present theory to the experimental results of PrPb and point out some future problems in this direction of research.

11 pages, 7 Postscript figures, accepted for publication in J. Phys. Soc. Jpn

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