arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1202.3203cond-mat.str-el
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二维拓扑绝缘体中相关效应的研究

A study on correlation effects in two dimensional topological insulators

Y. Tada, R. Peters, M. Oshikawa, A. Koga, N. Kawakami, S. Fujimoto

摘要:

研究了二维拓扑绝缘体(TI)中的相关效应。在第一部分中,我们讨论了带状几何中不同尺寸相互作用系统的有限尺寸效应。对于大系统,在两个边缘上有两对分离良好的无质量模式。对于这些系统,我们使用标准玻色子化方法分析有限尺寸效应。对于边缘态为大质量Dirac费米子的小系统,我们采用非均匀动力学平均场论(DMFT)结合迭代微扰理论作为杂质求解器来研究相互作用效应。我们发现,有限尺寸的间隙在边缘状态的重正化弱相互作用,这是符合费米液体图片小尺寸TI。在第二部分中,我们研究了有限尺寸TI在零温度下的相变,重点是使用数值重整化群研究非均匀DMFT中边缘态的边缘间Umklapp散射的影响。我们发现,相关效应是有效的更强的边缘附近的网站,因为配位数是小于在散装。因此,边缘站点周围的边缘状态的本地化,这是一个基本的属性在TI,被削弱强耦合强度。然而,我们没有发现任何迹象的“边缘莫特绝缘状态”和系统停留在拓扑绝缘状态,这是示意性地连接到非相互作用状态,所有的相互作用强度小于临界值。进一步增加相互作用,几乎均匀的莫特绝缘状态是稳定的。

英文摘要:

We investigate correlation effects in two dimensional topological insulators (TI). In the first part, we discuss finite size effects for interacting systems of different sizes in a ribbon geometry. For large systems, there are two pairs of well separated massless modes on both edges. For these systems, we analyze the finite size effects using a standard bosonization approach. For small systems, where the edge states are massive Dirac fermions, we use the inhomogeneous dynamical mean field theory (DMFT) combined with iterative perturbation theory as an impurity solver to study interaction effects. We show that the finite size gap in the edge states is renormalized for weak interactions, which is consistent with a Fermi-liquid picture for small size TIs. In the second part, we investigate phase transitions in finite size TIs at zero temperature focusing on the effects of possible inter-edge Umklapp scattering for the edge states within the inhomogeneous DMFT using the numerical renormalization group. We show that correlation effects are effectively stronger near the edge sites because the coordination number is smaller than in the bulk. Therefore, the localization of the edge states around the edge sites, which is a fundamental property in TIs, is weakened for strong coupling strengths. However, we find no signs for "edge Mott insulating states" and the system stays in the topological insulating state, which is adiabatically connected to the non-interacting state, for all interaction strengths smaller than the critical value. Increasing the interaction further, a nearly homogeneous Mott insulating state is stabilized.

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