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Hidden order and multipolar exchange striction in a correlated f-electron system

Leonid V. Pourovskii1,2*, Sergii Khmelevskyi3

1 CPHT, Ecole Polytechnique, CNRS, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France

2 Coll├Ęge de France, 11 place Marcelin Berthelot, 75005 Paris, France

3 Research Center for Computational Materials Science and Engineering, Vienna University of Technology, Karlsplatz 13, 1040 Vienna, Austria

* Corresponding authors emails: leonid@cpht.polytechnique.fr
DOI10.24435/materialscloud:12-7q [version v1]

Publication date: Mar 18, 2021

How to cite this record

Leonid V. Pourovskii, Sergii Khmelevskyi, Hidden order and multipolar exchange striction in a correlated f-electron system, Materials Cloud Archive 2021.45 (2021), doi: 10.24435/materialscloud:12-7q.


The nature of order in low-temperature phases of some materials is not directly seen by experiment. Such "hidden orders" (HO) may inspire decades of research to identify the mechanism underlying those exotic states of matter. In insulators, HO phases originate in degenerate many-electron states on localized f or d shells that may harbor high-rank multipole moments. Coupled by inter-site exchange, those moments form a vast space of competing order parameters. Here, we show how the ground state order and magnetic excitations of a prototypical HO system, neptunium dioxide NpO2, can be fully described by a low-energy Hamiltonian derived by a many-body ab initio force theorem method. Superexchange interactions between the lowest crystal-field quadruplet of Np4+ ions induce a primary non-collinear order of time-odd rank-5 (triakontadipolar) moments with a secondary quadrupole order preserving the cubic symmetry of NpO2. Our study also reveals an unconventional multipolar exchange-striction mechanism behind the anomalous volume contraction of the NpO2 HO phase.

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427.5 KiB This archive contains data on calculated electronic structure, crystal-field splitting, exchange interactions, mean-field order parameters and inelastic neutron scattering (INS) cross-section of the neptunium dioxide NpO2 discussed in this manuscript.
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External references

Journal reference
L. V. Pourovskii, S. Khmelevskyi, PNAS (accepted)


strongly correlated electrons hidden order ab initio linear response effective Hamiltonians ERC

Version history:

2021.45 (version v1) [This version] Mar 18, 2021 DOI10.24435/materialscloud:12-7q