Hidden order and multipolar exchange striction in a correlated f-electron system
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...
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Published in | Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 14; pp. 1 - 8 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
National Academy of Sciences
06.04.2021
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Subjects | |
Online Access | Get full text |
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Summary: | 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. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Edited by Zachary Fisk, University of California, Irvine, CA, and approved January 7, 2021 (received for review December 9, 2020) 2L.V.P. and S.K. contributed equally to this work. Author contributions: L.V.P. and S.K. designed research, performed research, analyzed data, and wrote the paper. |
ISSN: | 0027-8424 1091-6490 1091-6490 |
DOI: | 10.1073/pnas.2025317118 |