Cluster rearrangement by chiral charge order in lacunar spinel GaNb$_4$Se$_8$
| Autor: | Kitou, Shunsuke, Gen, Masaki, Nakamura, Yuiga, Tokunaga, Yusuke, Arima, Taka-hisa |
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| Rok vydání: | 2024 |
| Předmět: | |
| Zdroj: | Chem. Mater. 2024 |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1021/acs.chemmater.4c00118 |
| Popis: | Transition-metal atoms with d electrons sometimes form clusters in crystals, which significantly affects the physical properties. Such a cluster formation frequently accompanies a change in the crystal system, leading to the presence of domains with different crystal orientations. In particular, the cubic symmetry is rarely retained after the cluster formation. Here, we identify a cubic-to-cubic phase transition in lacunar spinel GaNb$_4$Se$_8$, where the change in the lattice parameter is less than 0.0001%. Each Nb$^{3.25+}$ tetramer with seven 4d electrons is distorted into a Nb$^{3+}$ trimer and a Nb$^{4+}$ monomer induced by charge disproportionation among Nb ions. While the Nb$^{3+}$ trimer with six 4d electrons forms spin-singlets in the sigma-bonding orbitals for three Nb-Nb bonds, a localized S=1/2 spin remains on the Nb$^{4+}$ ion. Furthermore, a local electric dipole moment is induced along the three-fold rotation axis of each distorted tetramer by the cluster rearrangement. The electric dipole moments are regularly arranged to maintain the cubic symmetry, giving rise to chiral order. Comment: 24 pages, 4 figures, supporting information |
| Databáze: | arXiv |
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