Structural studies on $A_2$ReCl$_6$ ($A$=K, Rb, Cs): absence of Jahn-Teller distortion
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| Format: | Preprint |
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2026
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| author | Bertin, A. Kiefer, L. Pomjakushin, V. Fabelo, O. Becker, P. Bohaty, L. Braden, M. |
| author_facet | Bertin, A. Kiefer, L. Pomjakushin, V. Fabelo, O. Becker, P. Bohaty, L. Braden, M. |
| contents | K$_2$ReCl$_6$ belongs to the antifluorite family and exhibits a sequence of structural transitions above the onset of magnetic order at $T_N$ = 12 K. Because of its 5d3 electronic configuration in an octahedral coordination, the ground state is a pure spin state without orbital degeneracy within the LS coupling scheme, but it can become Jahn-Teller active in the strong spin-orbit coupling limit described by the $jj$ coupling [S. Streltsov and D. I. Khomskii, Phys. Rev. X 10, 031043 (2020)]. While the structural transitions in K$_2$ReCl$_6$ are understood in terms of octahedral rotation and tilting, the possible impact of a Jahn-Teller distortion remains an open issue. We report on comprehensive crystalstructure studies by means of powder neutron and single-crystal x-ray diffraction on K$_2$ReCl$_6$ and on K$_2$SnCl$_6$. The latter material is used as a reference, because it exhibits the same sequence of structural transitions as K$_2$ReCl$_6$, but possesses a filled 4d shell ruling out a Jahn-Teller distortion. While the ReCl$_6$ octahedron in K$_2$ReCl$_6$ presents sizable distortions at intermediate temperatures, there is no such distortion persisting to low temperatures excluding a sizable Jahn-Teller effect. Studies on polycrystalline samples of Rb$_2$ReCl$_6$ and Cs$_2$ReCl$_6$, in which the structural transitions are suppressed due to the larger alkaline ionic radius, also do not find any indications for a Jahn-Teller distortion. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2602_08665 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Structural studies on $A_2$ReCl$_6$ ($A$=K, Rb, Cs): absence of Jahn-Teller distortion Bertin, A. Kiefer, L. Pomjakushin, V. Fabelo, O. Becker, P. Bohaty, L. Braden, M. Strongly Correlated Electrons K$_2$ReCl$_6$ belongs to the antifluorite family and exhibits a sequence of structural transitions above the onset of magnetic order at $T_N$ = 12 K. Because of its 5d3 electronic configuration in an octahedral coordination, the ground state is a pure spin state without orbital degeneracy within the LS coupling scheme, but it can become Jahn-Teller active in the strong spin-orbit coupling limit described by the $jj$ coupling [S. Streltsov and D. I. Khomskii, Phys. Rev. X 10, 031043 (2020)]. While the structural transitions in K$_2$ReCl$_6$ are understood in terms of octahedral rotation and tilting, the possible impact of a Jahn-Teller distortion remains an open issue. We report on comprehensive crystalstructure studies by means of powder neutron and single-crystal x-ray diffraction on K$_2$ReCl$_6$ and on K$_2$SnCl$_6$. The latter material is used as a reference, because it exhibits the same sequence of structural transitions as K$_2$ReCl$_6$, but possesses a filled 4d shell ruling out a Jahn-Teller distortion. While the ReCl$_6$ octahedron in K$_2$ReCl$_6$ presents sizable distortions at intermediate temperatures, there is no such distortion persisting to low temperatures excluding a sizable Jahn-Teller effect. Studies on polycrystalline samples of Rb$_2$ReCl$_6$ and Cs$_2$ReCl$_6$, in which the structural transitions are suppressed due to the larger alkaline ionic radius, also do not find any indications for a Jahn-Teller distortion. |
| title | Structural studies on $A_2$ReCl$_6$ ($A$=K, Rb, Cs): absence of Jahn-Teller distortion |
| topic | Strongly Correlated Electrons |
| url | https://arxiv.org/abs/2602.08665 |