Pourovskii, L. V., & Khmelevskyi, S. (2021). Hidden order and multipolar exchange striction in a correlated f-electron system. Proceedings of the National Academy of Sciences of the United States of America, 118(14), Article e2025317118. https://doi.org/10.1073/pnas.2025317118
E057-15 - Fachbereich Center for Computational Materials Science and Engineering
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Zeitschrift:
Proceedings of the National Academy of Sciences of the United States of America
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ISSN:
0027-8424
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Datum (veröffentlicht):
Apr-2021
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Umfang:
8
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Verlag:
National Academy of Sciences
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Peer Reviewed:
Ja
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Keywords:
Multidisciplinary; strongly correlated electrons; hidden order; ab initio; linear response; effective Hamiltonians
en
Abstract:
The nature of order in low-temperature phases of some materials is not directly seen by experiment. Such “hidden orders” (HOs) 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 intersite 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 noncollinear 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.
