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arXiv 1909.09425cond-mat.str-elcond-mat.stat-mech
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钙硼矿中Dzyaloshinskiii-Moriya相互作用的影响:磁序和热霍尔效应

Effects of Dzyaloshinskii-Moriya interactions in volborthite: Magnetic orders and thermal Hall effect

Shunsuke Furukawa, Tsutomu Momoi

摘要:

Volborthite提供了一个有趣的例子,一个高度受挫的量子磁体,其中铁磁和反铁磁相互作用在各向异性的戈薇晶格上竞争。最近的密度泛函理论计算提供了一个基于耦合三聚体的磁性模型,这与实验观察到的宽的1/3磁化平台是一致的。在这里,我们研究的Dzyaloshinskiii-Moriya(DM)的相互作用在伏硼硫石的影响。我们推导出一个有效的模型,其中出现在三聚体上的赝自旋1/2矩形成各向异性三角晶格的网络。使用有效的模型,我们表明,对于一个磁场垂直于kagome层,磁振子激发从1/3平台感到由于DM相互作用的Berry曲率,从而引起热霍尔效应。我们的磁振子玻色气体理论可以解释实验测量的磁化强度和霍尔热导率的定性特征。与实验的进一步定量比较对有效模型中的耦合常数提出了限制,促进了准一维图像。在此基础上,利用有效场论分析了低温磁相图,指出了磁场方向对低温磁相图的重要影响。

英文摘要:

Volborthite offers an interesting example of a highly frustrated quantum magnet in which ferromagnetic and antiferromagnetic interactions compete on anisotropic kagome lattices. A recent density functional theory calculation has provided a magnetic model based on coupled trimers, which is consistent with a broad 1/3-magnetization plateau observed experimentally. Here we study the effects of Dzyaloshinskii-Moriya (DM) interactions in volborthite. We derive an effective model in which pseudospin-1/2 moments emerging on trimers form a network of an anisotropic triangular lattice. Using the effective model, we show that for a magnetic field perpendicular to the kagome layer, magnon excitations from the 1/3-plateau feel a Berry curvature due to the DM interactions, giving rise to a thermal Hall effect. Our magnon Bose gas theory can explain qualitative features of the magnetization and the thermal Hall conductivity measured experimentally. A further quantitative comparison with experiment poses constraints on the coupling constants in the effective model, promoting a quasi-one-dimensional picture. Based on this picture, we analyze low-temperature magnetic phase diagrams using effective field theory, and point out their crucial dependence on the field direction.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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