Quantum magnetic phase transitions in a Kugel-Khomskii model including spin-orbit coupling
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| Format: | Preprint |
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2026
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| _version_ | 1866910034065096704 |
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| author | Chizhov, D. E. Igoshev, P. A. Irkhin, V. Yu. |
| author_facet | Chizhov, D. E. Igoshev, P. A. Irkhin, V. Yu. |
| contents | Using the formalism of pseudospin and isospin operators the Hamiltonian of an effective Kugel-Khomskii model with spin-orbit coupling is derived with an exact account of the $t_{2g}$ multiplet splitting by the crystal field. An analytical solution is obtained for an arbitrary relation between the Hubbard repulsion and crystal field splitting, i.e., interpolating the cases of Mott-Hubbard and charge-transfer insulators. A description of orbital orders is given in terms of octupole moments. The ground-state phase diagram is constructed in the parameter space spanned by spin-orbit coupling, Hund's exchange, and Hubbard interaction. We investigate a quantum phase transition between a state exhibiting hidden magnetic and orbital long-range order and a ferromagnetic state with a reduced magnetic moment accompanied by antiferroorbital order. It is shown that the cooperative effect of Hund's and spin-orbit interactions gives rise to an easy-plane-type anisotropy. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2602_23011 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Quantum magnetic phase transitions in a Kugel-Khomskii model including spin-orbit coupling Chizhov, D. E. Igoshev, P. A. Irkhin, V. Yu. Strongly Correlated Electrons Materials Science Using the formalism of pseudospin and isospin operators the Hamiltonian of an effective Kugel-Khomskii model with spin-orbit coupling is derived with an exact account of the $t_{2g}$ multiplet splitting by the crystal field. An analytical solution is obtained for an arbitrary relation between the Hubbard repulsion and crystal field splitting, i.e., interpolating the cases of Mott-Hubbard and charge-transfer insulators. A description of orbital orders is given in terms of octupole moments. The ground-state phase diagram is constructed in the parameter space spanned by spin-orbit coupling, Hund's exchange, and Hubbard interaction. We investigate a quantum phase transition between a state exhibiting hidden magnetic and orbital long-range order and a ferromagnetic state with a reduced magnetic moment accompanied by antiferroorbital order. It is shown that the cooperative effect of Hund's and spin-orbit interactions gives rise to an easy-plane-type anisotropy. |
| title | Quantum magnetic phase transitions in a Kugel-Khomskii model including spin-orbit coupling |
| topic | Strongly Correlated Electrons Materials Science |
| url | https://arxiv.org/abs/2602.23011 |