自旋1基泰格磁体中的手性玻色平均场Ansatz与自旋动力学
Chiral bosonic mean-field Ansatz and spin dynamics in spin-1 Kitaev magnets
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中文总结 AI 辅助
本研究针对自旋1基泰格模型，扩展三重态π/2通量手性玻色平均场Ansatz分析至弱非对角交换，计算自旋结构因子并验证其对自旋动力学的描述有效性。
中文摘要 AI 辅助
基泰格模型是实现量子自旋液体的典型体系，但其高自旋扩展无法精确求解，自旋动力学的研究也不如自旋1/2情形透彻。本研究重新考察了此前提出的反铁磁S=1基泰格模型的三重态配对φ_t=π/2相模式，并将分析扩展至弱对称非对角交换Γ和Γ'。采用施温格玻色平均场理论的键算符形式，针对适用于基泰格相互作用的自旋关联方案，计算了三重态0通量和三重态π/2通量Ansatz的动力学自旋结构因子。在纯基泰格极限下，π/2通量Ansatz产生的谱比0通量Ansatz更平坦；实空间自旋关联显示，π/2通量Ansatz比0通量Ansatz更强地抑制长程关联，得到的关联模式更接近纯基泰格极限下预期的短程形式。该对比表明，S(q,ω)的平坦性与短程自旋关联相关，是重要的一致性检验，但本身并非时间反演对称性破缺的判据。随后，在纯基泰格极限附近取Γ'=Γ的弱非对角交换，参考候选自旋1基泰格材料分析得到的同号关系，研究了受限π/2通量流形内的有隙解，其谱具有有限尺寸精确对角化发现的定性能量和动量空间特征。综合来看，这些结果支持三重态π/2通量手性玻色Ansatz可作为弱非对角交换下反铁磁S=1基泰格极限附近自旋动力学的有效平均场描述。
英文摘要
The Kitaev model is a paradigmatic system for realizing quantum spin liquids, but its higher-spin extensions are not exactly solvable, and their spin dynamics is less well understood than in the spin-1/2 case. In this work, we reexamine a previously introduced triplet-pairing $ϕ_t = π/2$ phase pattern for the antiferromagnetic $S = 1$ Kitaev model and extend the analysis to weak symmetric off-diagonal exchanges $Γ$ and $Γ'$. Using a bond-operator formulation of Schwinger-boson mean-field theory, we calculate the dynamical spin structure factor for the triplet 0-flux and triplet $π/2$-flux Ansätze with a spin-correlation scheme appropriate for Kitaev interactions. In the pure Kitaev limit, the $π/2$-flux Ansatz yields a flatter spectrum than the 0-flux Ansatz. The real-space spin correlations show that the $π/2$-flux Ansatz suppresses longer-distance correlations more strongly than the 0-flux Ansatz, yielding a correlation pattern closer to the short-ranged form expected in the Kitaev limit. This comparison shows that the flatness of $S(\boldsymbol{q}, ω)$ is tied to short-ranged spin correlations and is therefore an important consistency check, although it is not, by itself, a diagnostic of time-reversal-symmetry breaking. We then study weak off-diagonal exchanges along $Γ' = Γ$ near the pure Kitaev limit, taking the same-sign relation from analyses of candidate spin-1 Kitaev materials. Gapped solutions are obtained within the constrained $π/2$-flux manifold, and the spectra share the qualitative energy- and momentum-space features found by finite-size exact diagonalization. Taken together, these results support the triplet $π/2$-flux chiral bosonic Ansatz as a useful mean-field description of spin dynamics near the antiferromagnetic $S = 1$ Kitaev limit with weak off-diagonal exchanges.
