arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1507.06307cond-mat.str-el
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受抑三角系统Kitaev极限附近的磁序:对Ba $_3$ IrTi $_2$ O $_9$的应用

Magnetic Orders Proximal to the Kitaev Limit in Frustrated Triangular Systems: Application to Ba$_3$IrTi$_2$O$_9$

Andrei Catuneanu, Jeffrey G. Rau, Heung-Sik Kim, Hae-Young Kee

摘要:

近年来,自旋轨道耦合(SOC)和电子关联共同作用的阻挫过渡金属化合物引起了人们的广泛关注。在5 $d$过渡金属的情况下,其中SOC很大,费米能级附近的$j_\text{eff}=1/2$带被认为包含材料的基本物理性质,可能导致具体实现奇异磁相,如Kitaev自旋液体。在这里,我们推导出一个基于$j_\text{eff} = 1/2$赝自旋的三角晶格上的自旋模型,该赝自旋通过反铁磁海森堡($J$)和Kitaev($K$)交换相互作用,并且关键的是,各向异性$(Γ)$交换。我们对自旋模型的经典分析表明,除了120 $^\circ$、$\mathbb{Z}_2$ /双$\mathbb{Z}_2$涡旋晶体和双晶相的小区域外,条纹相和铁磁相在$J$ - $K$ - $Γ$相图中占主导地位。我们将我们的模型应用于5 $d$过渡金属化合物,Ba $_3$ IrTi $_2$ O $_9$,其中Ir $^{4+}$离子形成分层的二维三角晶格。我们计算的能带结构和最近邻跳跃参数使用从头计算。结合我们的从头算和经典分析,我们预测Ba $_3$ IrTi $_2$ O $_9$具有条纹有序的磁性基态。

英文摘要:

Frustrated transition metal compounds in which spin-orbit coupling (SOC) and electron correlation work together have attracted much attention recently. In the case of 5$d$ transition metals, where SOC is large, $j_\text{eff}=1/2$ bands near the Fermi level are thought to encompass the essential physics of the material, potentially leading to a concrete realization of exotic magnetic phases such as the Kitaev spin liquid. Here we derive a spin model on a triangular lattice based on $j_\text{eff} = 1/2$ pseudospins that interact via antiferromagnetic Heisenberg ($J$) and Kitaev ($K$) exchanges, and crucially, an anisotropic $(Γ)$ exchange. Our classical analysis of the spin model reveals that, in addition to small regions of 120$^\circ$, $\mathbb{Z}_2$ / dual-$\mathbb{Z}_2$ vortex crystal and nematic phases, the stripy and ferromagnetic phases dominate the $J$-$K$-$Γ$ phase diagram. We apply our model to the 5$d$ transition metal compound, Ba$_3$IrTi$_2$O$_9$, in which the Ir$^{4+}$ ions form layered two-dimensional triangular lattices. We compute the band structure and nearest-neighbor hopping parameters using ab-initio calculations. By combining our ab-initio and classical analyses, we predict that Ba$_3$IrTi$_2$O$_9$ has a stripy ordered magnetic ground state.

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