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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2601.18469 |
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| _version_ | 1866918305643626496 |
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| author | Hong, Seung-Ju Kim, Tae Yun Park, Cheol-Hwan |
| author_facet | Hong, Seung-Ju Kim, Tae Yun Park, Cheol-Hwan |
| contents | $α$-RuCl$_3$ is a candidate Kitaev material that exhibits zigzag antiferromagnetic ordering below 7 K. One contentious issue regarding this material is its bulk structure in the low-temperature phase. Recently, it has become generally accepted from experiments that the low- and high-temperature structures belong to the $R\bar{3}$ and $C2/m$ space groups, respectively. However, there was no theoretical study supporting the $R\bar{3}$-type structure as the low-temperature structure. In this study, we use constrained density functional theory to show that the $R\bar{3}$ structure is lower in energy than the $C2/m$ structure, in agreement with experimental observations. Then, we show that the conduction band minimum states are almost of the $J_\textrm{eff}=1/2$ and $m_\textrm{eff}=-1/2$ character, if we set the angular momentum quantization axis to be parallel to the Néel vector; this is the first analysis of the $J_\textrm{eff}$ picture for $α$-RuCl$_3$ from this perspective. In addition, we compute the anisotropic magnetic exchange parameters and $g$ factors of monolayer $α$-RuCl$_3$, thereby providing a comprehensive understanding of its magnetism. Our results demonstrate that both second-nearest-neighbor exchange interactions and magnetic moments not captured by the conventional atomic orbital projection method are necessary for accurate description of the magnetism in $α$-RuCl$_3$. Moreover, the calculated $g$ factors are in fairly good agreement with experimental measurements, especially the small anisotropy between their in-plane and out-of-plane components. Finally, we examine the effects of structural distortions from a perfect RuCl$_6$ octahedron, already present in bulk $α$-RuCl$_3$ without any external perturbation, on the magnetic properties. (The abstract is cut here due to the word limit; see the pdf file for the full abstract.) |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2601_18469 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | First-principles study of bulk stacking, $J_{\rm eff}$ picture, magnetic Hamiltonian, $g$ factors, and structural distortions of $α$-RuCl$_3$ Hong, Seung-Ju Kim, Tae Yun Park, Cheol-Hwan Materials Science $α$-RuCl$_3$ is a candidate Kitaev material that exhibits zigzag antiferromagnetic ordering below 7 K. One contentious issue regarding this material is its bulk structure in the low-temperature phase. Recently, it has become generally accepted from experiments that the low- and high-temperature structures belong to the $R\bar{3}$ and $C2/m$ space groups, respectively. However, there was no theoretical study supporting the $R\bar{3}$-type structure as the low-temperature structure. In this study, we use constrained density functional theory to show that the $R\bar{3}$ structure is lower in energy than the $C2/m$ structure, in agreement with experimental observations. Then, we show that the conduction band minimum states are almost of the $J_\textrm{eff}=1/2$ and $m_\textrm{eff}=-1/2$ character, if we set the angular momentum quantization axis to be parallel to the Néel vector; this is the first analysis of the $J_\textrm{eff}$ picture for $α$-RuCl$_3$ from this perspective. In addition, we compute the anisotropic magnetic exchange parameters and $g$ factors of monolayer $α$-RuCl$_3$, thereby providing a comprehensive understanding of its magnetism. Our results demonstrate that both second-nearest-neighbor exchange interactions and magnetic moments not captured by the conventional atomic orbital projection method are necessary for accurate description of the magnetism in $α$-RuCl$_3$. Moreover, the calculated $g$ factors are in fairly good agreement with experimental measurements, especially the small anisotropy between their in-plane and out-of-plane components. Finally, we examine the effects of structural distortions from a perfect RuCl$_6$ octahedron, already present in bulk $α$-RuCl$_3$ without any external perturbation, on the magnetic properties. (The abstract is cut here due to the word limit; see the pdf file for the full abstract.) |
| title | First-principles study of bulk stacking, $J_{\rm eff}$ picture, magnetic Hamiltonian, $g$ factors, and structural distortions of $α$-RuCl$_3$ |
| topic | Materials Science |
| url | https://arxiv.org/abs/2601.18469 |