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Microscopic theory of multipole ordering in NpO2

Katsunori Kubo·Takashi Hotta
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Abstract

In order to examine the mysterious ordered phase of NpO2 from a microscopic viewpoint, we investigate an f-electron model on an fcc lattice constructed based on a j-j coupling scheme. First, an effective model with multipole interactions is derived in the strong-coupling limit. Numerical analysis of the model clearly indicates that the interactions for Γ_{4u} and Γ_{5u} moments are relevant to the ground state. Then, by applying mean-field theory to the simplified model including only such interactions, we conclude that longitudinal triple-q Γ_{5u} octupole order is realized in NpO2 through the combined effects of multipole interactions and anisotropy of the Γ_{5u} moment.

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Katsunori Kubo, Takashi Hotta. 2005-04-30. Microscopic theory of multipole ordering in NpO2. https://doi.org/10.1103/physrevb.71.140404

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