论文标题
$ d^{5} $ kitaev材料中的交换交互材料：na $ _2 $ iro $ _3 $ to $α$ -rucl $ _3 $
Exchange interactions in $d^{5}$ Kitaev materials: From Na$_2$IrO$_3$ to $α$-RuCl$_3$
论文作者
论文摘要
我们介绍了一项分析性研究，对伪旋转一半$ d^{5} $ ions之间的交换相互作用与边缘共享的八面体。考虑了涉及Hubbard U，电荷转移激发和环状交换的各种交换渠道。包括$ t_ {2g} $ orbitals以及$ t_ {2g} $和$ e_g $ orbitals中的hoppings。特别注意三角晶体场$δ$对交换参数的影响。获得的交换Hamiltonian在$δ$范围内的铁磁相互作用K所主导。已经发现，接近电荷转移绝缘子状态的参数区域和小$δ$最有希望实现Kitaev旋转液相。基于我们的理论，讨论了两种代表性的蜂窝材料NA $ _2 $ IRO $ _3 $和$α$ -RUCL $ _3 $。我们发现，两种材料具有主导的铁磁K和阳性非对角线$γ$值。但是，他们的Heisenberg J术语具有相反的符号：afm j> 0 in Na $ _2 $ IRO $ _3 $和fm j <0 in $α$ -rucl $ _3 $。这带来了不同的磁波动，并导致其不同的磁化行为和自旋激发光谱。由于$α$ -rucl $ _3 $，强调与FM状态的距离。这两种材料的交换耦合之间的差异源自相对的$δ$值，表明晶体场可以用作有效的控制参数，以调整$ d^{5} $ spin-orbit mott mott mott iSulators的磁性。
We present an analytical study of the exchange interactions between pseudospin one-half $d^{5}$ ions in honeycomb lattices with edge-shared octahedra. Various exchange channels involving Hubbard U, charge-transfer excitations, and cyclic exchange are considered. Hoppings within $t_{2g}$ orbitals as well as between $t_{2g}$ and $e_g$ orbitals are included. Special attention is paid to the trigonal crystal field $Δ$ effects on the exchange parameters. The obtained exchange Hamiltonian is dominated by ferromagnetic Kitaev interaction K within a wide range of $Δ$. It is found that a parameter region close to the charge-transfer insulator regime and with a small $Δ$ is most promising to realize the Kitaev spin liquid phase. Two representative honeycomb materials Na$_2$IrO$_3$ and $α$-RuCl$_3$ are discussed based on our theory. We have found that both materials share dominant ferromagnetic K and positive non-diagonal $Γ$ values. However, their Heisenberg J terms have opposite signs: AFM J>0 in Na$_2$IrO$_3$ and FM J<0 in $α$-RuCl$_3$. This brings different magnetic fluctuations and results in their different magnetization behaviors and spin excitation spectra. Proximity to FM state due to the large FM J is emphasized in $α$-RuCl$_3$. The differences between the exchange couplings of these two materials originate from the opposite $Δ$ values, indicating that the crystal field can serve as an efficient control parameter to tune the magnetic properties of $d^{5}$ spin-orbit Mott insulators.
