Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate α-RuCl_3
Evidence for Magnetic Fractional Excitations in a Kitaev Quantum-Spin-Liquid Candidate α-RuCl_3
复制标题
Kitaev 量子自旋液体候选 α-RuCl3 中磁分数激发的证据
DOI：
10.1088/0256-307x/39/2/027501
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发表时间：
2022
影响因子：
3.5
通讯作者：
Wen Jinsheng
中科院分区：
文献类型：
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作者：
Ran Kejing;Wang Jinghui;Bao Song;Cai Zhengwei;Shangguan Yanyan;Ma Zhen;Wang Wei;Dong Zhaoyang;Cermak P;Schneidewind A;Meng Siqin;Lu Zhilun;Yu Shunli;Li Jianxin;Wen Jinsheng
众所周知，α-RuCl 3已经被广泛研究，因为它接近Kitaev量子自旋液体（QSL）相，并且可以通过调节竞争相互作用来接近它。本文首次对α-RuCl 3单晶进行了极化非弹性中子散射研究，以探索布里渊区中心Γ点附近的散射连续体，该散射连续体被假设为Kitaev QSL态的结果，但没有具体的证据。通过极化分析，我们发现，当M点附近的自旋波激发在转变温度TN以上消失时，Γ点附近的纯磁连续激发对温度具有鲁棒性。此外，通过用团簇微扰理论计算自旋-自旋动力学关联函数，我们得到了基于K-Γ模型的磁色散谱，其中包含了-7.2meV的铁磁Kitaev相互作用和5.6meV的非对角相互作用.我们发现该模型不仅能再现M点附近的自旋波激发谱，而且能再现Γ点附近的非自旋波连续磁激发谱。这些结果为Kitaev QSL态在Γ点附近存在分数激发提供了证据，并进一步支持K-Γ模型作为描述α-RuCl 3的有效最小自旋模型的有效性.
It is known that α-RuCl 3 has been studied extensively because of its proximity to the Kitaev quantum-spin-liquid (QSL) phase and the possibility of approaching it by tuning the competing interactions. Here we present the first polarized inelastic neutron scattering study on α-RuCl 3 single crystals to explore the scattering continuum around the Γ point at the Brillouin zone center, which was hypothesized to be resulting from the Kitaev QSL state but without concrete evidence. With polarization analyses, we find that, while the spin-wave excitations around the M point vanish above the transition temperature T N, the pure magnetic continuous excitations around the Γ point are robust against temperature. Furthermore, by calculating the dynamical spin-spin correlation function using the cluster perturbation theory, we derive magnetic dispersion spectra based on the K–Γ model, which involves with a ferromagnetic Kitaev interaction of–7.2 meV and an off-diagonal interaction of 5.6 meV. We find this model can reproduce not only the spin-wave excitation spectra around the M point, but also the non-spin-wave continuous magnetic excitations around the Γ point. These results provide evidence for the existence of fractional excitations around the Γ point originating from the Kitaev QSL state, and further support the validity of the K–Γ model as the effective minimal spin model to describe α-RuCl 3.