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arXiv · 2312.15932

Observation of a 1/3 Magnetisation Plateau Phase as Evidence for the Kitaev Interaction in a Honeycomb-Lattice Antiferromagnet

Yanyan Shangguan·Song Bao·Zhao-Yang Dong·Ning Xi·Yi-Peng Gao·Zhen Ma·Wei Wang·Zhongyuan Qi·Shuai Zhang·Zhentao Huang·Junbo Liao·Xiaoxue Zhao·Bo Zhang·Shufan Cheng·Hao Xu·Dehong Yu·Richard A. Mole·Naoki Murai·Seiko Ohira-Kawamura·Lunhua He·Jiazheng Hao·Qing-Bo Yan·Fengqi Song·Wei Li·Shun-Li Yu·Jian-Xin Li·Jinsheng Wen
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Abstract

Fractional magnetisation plateaus, in which the magnetisation is pinned at a fraction of its saturated value within a range of external magnetic field, are spectacular macroscopic manifestations of the collective quantum behaviours. One prominent example of the plateau phase is found in spin-1/2 triangular-lattice antiferromagnets featuring strong geometrical frustration, and is often interpreted as quantum-fluctuation-stabilised state in magnetic field via the "order-by-disorder" mechanism. Here, we observe an unprecedented 1/3 magnetisation plateau between 5.2 and 7.4 T at 2 K in a spin-1 antiferromagnet Na$_3$Ni$_2$BiO$_6$ with a honeycomb lattice, where conventionally no geometrical frustration is anticipated. By carrying out elastic neutron scattering measurements, we propose the spin structure of the plateau phase to be an unusual partial spin-flop ferrimagnetic order, transitioning from the zigzag antiferromagnetic order in zero field. Our theoretical calculations show that the plateau phase is stabilised by the bond-anisotropic Kitaev interaction. These results provide a new paradigm for the exploration of rich quantum phases in frustrated magnets and exotic Kitaev physics in high-spin systems.

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Yanyan Shangguan, Song Bao, Zhao-Yang Dong, Ning Xi, Yi-Peng Gao, Zhen Ma, Wei Wang, Zhongyuan Qi, Shuai Zhang, Zhentao Huang, Junbo Liao, Xiaoxue Zhao, Bo Zhang, Shufan Cheng, Hao Xu, Dehong Yu, Richard A. Mole, Naoki Murai, Seiko Ohira-Kawamura, Lunhua He, Jiazheng Hao, Qing-Bo Yan, Fengqi Song, Wei Li, Shun-Li Yu, Jian-Xin Li, Jinsheng Wen. 2023-12-26. Observation of a 1/3 Magnetisation Plateau Phase as Evidence for the Kitaev Interaction in a Honeycomb-Lattice Antiferromagnet. https://doi.org/10.1038/s41567-023-02212-2

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