Magnetic ordering phenomena of interacting quantum spin Hall models
Magnetic ordering phenomena of interacting quantum spin Hall models
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DOI：
10.1103/physrevb.86.155127
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发表时间：
2012-06
影响因子：
3.7
通讯作者：
J. Reuther;R. Thomale;S. Rachel
中科院分区：
文献类型：
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作者：
J. Reuther;R. Thomale;S. Rachel
为表现量子自旋霍尔效应的拓扑带结构定义的二维Hubbard模型在唯象表征和微观分类方面提出了根本的挑战。在半填充无限耦合U的极限下，由强耦合展开产生的自旋模型哈密顿量根据自旋-轨道耦合项的不同表现出不同形式的磁有序现象。我们研究了具有z轴本征自旋-轨道耦合的Kane-Mele Hubbard模型的无限U极限，以及它对一般的多方向自旋轨道项的推广，该项被认为可以解释单层Na2IrO_3中的物理场景。我们发现，当我们改变自旋轨道耦合强度时，保持在前者中而在后者中被破坏的轴自旋对称性对磁相图有根本的影响。虽然Kane-Mele自旋模型显示了从传统的蜂窝Neel到XY反铁磁性的连续演化，从而避免了自旋-轨道耦合增加带来的阻碍，但多方向的自旋-轨道项在中等耦合强度下诱导了相称到无公度的跃迁，并在无限自旋-轨道耦合的极限下产生了具有72位单胞的复杂螺旋态。根据我们的发现，我们推测，在轴自旋对称性破缺的情况下，在足够大的自旋-轨道耦合和中间U处有很大的增加相的倾向。
The two-dimensional Hubbard model defined for topological band structures exhibiting a quantum spin Hall effect poses fundamental challenges in terms of phenomenological characterization and microscopic classification. In the limit of infinite coupling U at half filling, the spin model Hamiltonians resulting from a strong coupling expansion show various forms of magnetic ordering phenomena depending on the underlying spin-orbit coupling terms. We investigate the infinite U limit of the Kane-Mele Hubbard model with z-axis intrinsic spin-orbit coupling as well as its generalization to a generically multi-directional spin orbit term which has been claimed to account for the physical scenario in monolayer Na2IrO3. We find that the axial spin symmetry which is kept in the former but broken in the latter has a fundamental impact on the magnetic phase diagram as we vary the spin orbit coupling strength. While the Kane-Mele spin model shows a continuous evolution from conventional honeycomb Neel to XY antiferromagnetism which avoids the frustration imposed by the increased spin-orbit coupling, the multi-directional spin-orbit term induces a commensurate to incommensurate transition at intermediate coupling strength, and yields a complex spiral state with a 72 site unit cell in the limit of infinite spin-orbit coupling. From our findings, we conjecture that in the case of broken axial spin symmetry there is a large propensity for an additional phase at sufficiently large spin-orbit coupling and intermediate U.