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Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects

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GOTFRYD Dorota RUSNAČKO Juraj WOHLFELD Krzysztof JACKELI George CHALOUPKA Jiří OLEŚ Andrzej Michal

Druh Článek v odborném periodiku
Časopis / Zdroj Physical Review B
Fakulta / Pracoviště MU

Přírodovědecká fakulta

Citace
WWW https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.024426
Doi http://dx.doi.org/10.1103/PhysRevB.95.024426
Obor Fyzika pevných látek a magnetismus
Klíčová slova quantum magnetism; spin systems; frustration; spin liquid
Popis We explore the phase diagram of the Kitaev-Heisenberg model with nearest neighbor interactions on the honeycomb lattice using the exact diagonalization of finite systems combined with the cluster mean field approximation, and supplemented by the insights from analytic approaches: the linear spin-wave and second-order perturbation theories. This study confirms that by varying the balance between the Heisenberg and Kitaev term, frustrated exchange interactions stabilize in this model either one of four phases with magnetic long range order: Neel phase, ferromagnetic phase, and two other phases with coexisting antiferromagnetic and ferromagnetic bonds, zigzag and stripy phase, or one of two distinct spin-liquid phases. Out of these latter disordered phases, the one with ferromagnetic Kitaev interactions has a substantially broader range of stability as the neighboring competing ordered phases, ferromagnetic and stripy, have very weak quantum fluctuations. Focusing on the quantum spin-liquid phases, we study spatial spin correlations and dynamic spin structure factor of the model by the exact diagonalization technique, and discuss the evolution of gapped low-energy spin response across the quantum phase transitions between the disordered spin liquid and phases with long range magnetic order.
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