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arXiv 1704.06809cond-mat.str-el
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kagome量子反铁磁体中磁长程序的出现

Emergence of magnetic long-range order in kagome quantum antiferromagnets

Johannes Richter, Oliver Götze

摘要:

$s=1/2$海森堡可果梅反铁磁体(KAFM)的自旋液体基态的存在已被证实。同时,对于$s=1$海森堡KAFM,也发现了磁性长程序(LRO)不存在的证据,磁性LRO可以通过增加自旋量子数$s$到$s>1$而产生,而对于$s=1$,磁性LRO可以通过易面各向异性而产生.在本文中,我们讨论的路径磁有序的$s=1/2$ KAFMs包括一个各向同性层间耦合(ILC)$J_\perp$,以及一个易平面各向异性的kagome层中使用的耦合团簇方法的高阶近似。我们考虑铁磁以及反铁磁$J_\perp$。为了讨论从纯二维(2D)到准二维,最后到三维系统的交叉的一般问题,我们考虑最简单的堆叠(未移位)的可果美层模型。虽然真正的可果美化合物的ILC通常更复杂,但ILC的这种几何形状可能与巴洛石有关。我们发现,自旋液体基态目前严格的二维$s=1/2$ $XXZ$ KAFM生存有限的ILC,其中的自旋液体区域单调收缩的各向异性。如果ILC变得足够大(对于各向同性海森堡情况,约为层内耦合的15%,对于$XY$极限,约为4%),则可以建立磁性LRO,其中如果$J_\perp$具有中等强度,则$q=0$对称性是有利的。如果ILC的强度进一步增加,则$\sqrt{3}\times \sqrt{3}$ LRO可以变得对$q=0$ LRO有利。

英文摘要:

The existence of a spin-liquid ground state of the $s=1/2$ Heisenberg kagome antiferromagnet (KAFM) is well established. Meanwhile, also for the $s=1$ Heisenberg KAFM evidence for the absence of magnetic long-range order (LRO) was found. Magnetic LRO in Heisenberg KAFMs can emerge by increasing the spin quantum number $s$ to $s>1$ and for $s=1$ by an easy-plane anisotropy. In the present paper we discuss the route to magnetic order in $s=1/2$ KAFMs by including an isotropic interlayer coupling (ILC) $J_\perp$ as well as an easy-plane anisotropy in the kagome layers by using the coupled-cluster method to high orders of approximation. We consider ferro- as well as antiferromagnetic $J_\perp$. To discuss the general question for the crossover from a purely two-dimensional (2D) to a quasi-2D and finally to a three-dimensional system we consider the simplest model of stacked (unshifted) kagome layers. Although the ILC of real kagome compounds is often more sophisticated, such a geometry of the ILC can be relevant for barlowite. We find that the spin-liquid ground state present for the strictly 2D $s=1/2$ $XXZ$ KAFM survives a finite ILC, where the spin-liquid region shrinks monotonously with increasing anisotropy. If the ILC becomes large enough (about 15\% of intralayer coupling for the isotropic Heisenberg case and about 4\% for the $XY$ limit) magnetic LRO can be established, where the $q=0$ symmetry is favorable if $J_\perp$ is of moderate strength. If the strength of the ILC further increases, $\sqrt{3}\times \sqrt{3}$ LRO can become favorable against $q=0$ LRO.

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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