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arXiv 1605.07855cond-mat.str-el
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无反转对称蜂窝晶格和带状结构上的拓扑绝缘体

Topological insulator on honeycomb lattices and ribbons without inversion symmetry

Robert Triebl, Markus Aichhorn

摘要:

本文研究了具有对称性破缺项的Kane-Mele-哈伯德模型。利用拓扑哈密顿方法,我们计算了系统的$\mathbb{Z}_2$不变量随自旋轨道耦合、Hubbard相互作用$U$和反对称破缺在位势的变化.用这种方法计算的相图表明,一方面,后一种大项破坏了拓扑非平凡态。然而,另一方面,这种反转对称破缺场可以增强拓扑状态,因为对于中等值,从非平凡拓扑到平凡莫特绝缘体的过渡被推到更大的相互作用值$U$。这种增强的拓扑状态的特征也在蜂窝带上发现。利用反转对称性,对于任何值的$U$,Z字形带的边缘是磁性的。该磁矩破坏了无间隙边缘模式。提升反转对称性允许相互作用强度$U$中的有限区域,低于该区域存在无间隙边缘模式。

英文摘要:

We study the Kane-Mele-Hubbard model with an additional inversion-symmetry-breaking term. Using the topological Hamiltonian approach, we calculate the $\mathbb{Z}_2$ invariant of the system as function of spin-orbit coupling, Hubbard interaction $U$, and inversion-symmetry-breaking on-site potential. The phase diagram calculated in that way shows that, on the one hand, a large term of the latter kind destroys the topological non-trivial state. On the other hand, however, this inversion-symmetry-breaking field can enhance the topological state, since for moderate values the transition from the non-trivial topological to the trivial Mott insulator is pushed to larger values of interaction $U$. This feature of an enhanced topological state is also found on honeycomb ribbons. With inversion symmetry, the edge of the zigzag ribbon is magnetic for any value of $U$. This magnetic moment destroys the gapless edge mode. Lifting inversion symmetry allows for a finite region in interaction strength $U$ below which gapless edge modes exist.

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