论文标题

Kitaev模型的相图,用于任意磁场方向

Phase Diagrams of Kitaev Models for Arbitrary Magnetic-Field Orientations

论文作者

Yılmaz, F., Kampf, A. P., Yip, S. K.

论文摘要

Kitaev模型是在受约束的真实费米子语言中确切可解决的量子自旋模型。尽管沿特殊磁场方向进行了大量研究,但关于完整的场角表征的知识有限,可以提供有关分数化激发的存在的宝贵信息。为此,我们首先将先前关于铁磁Kitaev模型的现场角度响应的研究扩展到其抗磁磁性版本。然而,在边缘共享的八面体范式内,对候选吉塔夫材料的现实描述需要附加的耦合项,包括大型非对角线项$γ$以及可能的各向异性校正$γ_p$。因此,不足以依靠裸机模型的拓扑特性,是观察到的热霍尔电导率信号的唯一来源,并且需要对这些具有完整现场响应的扩展的基塔伊夫模型的理解。从现实的K- $γ$ - $γ_P$模型的零场相图开始,我们确定了反铁磁Zig-Zag和(部分)偏光相以及两个异常的Kitaev(-umγ$)旋转液体阶段。这些相对于任意场取向的磁场响应提供了非常丰富的相图。在两个有序的相位有限的磁化,有限的分数和有限的Chern数之间揭示了部分极化相。该阶段的特征是扩展的Kitaev-$γ$旋转液体。为了通过实验遵守我们的发现,我们在中间阶段的范围内专门针对两个不同的场方向$θ= \ pm 60^o $重现了不对称性。

The Kitaev model is an exactly solvable quantum spin model within the language of the constrained real fermions. In spite of numerous studies along special magnetic-field orientations, there is a limited amount of knowledge on the complete field-angle characterization, which can provide valuable information on the existence of fractionalized excitations. For this purpose, we first extend previous studies on the field-angle response of the ferromagnetic Kitaev model to its antiferromagnetic version. Yet, the realistic description of the candidate Kitaev materials, within the edge-sharing octahedra paradigm, require additional coupling terms, including a large off-diagonal term $Γ$ along with possible anisotropic corrections $Γ_p$. It is therefore not sufficient to depend on the topological properties of the bare Kitaev model as the only source for the observed thermal Hall conductivity signals and an understanding of these extended Kitaev models with a complete field response is demanded. Starting from the zero-field phase diagram of realistic K-$Γ$-$Γ_p$ models, we identify antiferromagnetic zig-zag and (partially) polarized phases as well as two unusual Kitaev(-$Γ$) spin-liquid phases. The magnetic field response of these phases for arbitrary field orientations provides a remarkably rich phase diagram. A partially polarized phase is revealed between two ordered phases with a suppressed magnetization, finite fractionalization and finite Chern number. This phase is characterized as an extended Kitaev-$Γ$ spin-liquid. To comply our findings with experiments, we reproduce the asymmetry in the extent of the intermediate phases specifically for the two different field directions $θ= \pm 60^o$.

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