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arXiv · 0906.3607

Microscopic analysis of multipole susceptibility of actinide dioxides: A scenario of multipole ordering in AmO$_2$

Takashi Hotta
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Abstract

By evaluating multipole susceptibility of a seven-orbital impurity Anderson model with the use of a numerical renormalization group method, we discuss possible multipole states of actinide dioxides at low temperatures. In particular, here we point out a possible scenario for multipole ordering in americium dioxide. For Am$^{4+}$ ion with five $5f$ electrons, it is considered that the ground state is $Γ_7^{-}$ doublet and the first excited state is $Γ_8^{-}$ quartet, but we remark that the $f^5$ ground state is easily converted due to the competition between spin-orbit coupling and Coulomb interactions. Then, we find that the $Γ_8^-$ quartet can be the ground state of AmO$_2$ even for the same crystalline electric field potential. In the case of $Γ_8^-$ quartet ground state, the numerical results suggest that high-order multipoles such as quadrupole and octupole can be relevant to AmO$_2$.

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Takashi Hotta. 2009-06-19. Microscopic analysis of multipole susceptibility of actinide dioxides: A scenario of multipole ordering in AmO$_2$. https://doi.org/10.1103/physrevb.80.024408

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