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arXiv 1404.4658cond-mat.str-el
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分数Chern绝缘体的单模近似和圆环面上的分数量子霍尔效应

The single-mode approximation for fractional Chern insulators and the fractional quantum Hall effect on the torus

C. Repellin, T. Neupert, Z. Papic, N. Regnault

摘要:

我们分析了玻色子Laughlin $ν=1/2$分数量子Hall(FWHH)态在环面上的集体磁-旋子激发,以及它们在晶格上的类似物,分数Chern绝缘体(FCI)的集体磁-旋子激发。我们表明,通过应用适当的映射的动量量子数之间的两个系统,磁-旋子模式可以确定在FCIs和它包含相同数量的状态,在CIMH的情况下。此外,我们数值测试的单模式近似的磁-旋子模式的两种情况下的FCI和FCI。这对FCI来说尤其具有挑战性,因为它的本征态比FCI的H-H态具有更低的平移对称性。尽管如此,我们构造FCI单模近似,使它携带相同的动量作为的OH-H状态,允许两个系统之间的直接比较。我们表明,单模近似捕获以及磁-旋子激发的色散子集的的CRASH和FCI的情况下。我们发现这两个系统之间的显着的定量协议。例如,多体激发能隙外推到热力学极限下几乎相同的值。

英文摘要:

We analyze the collective magneto-roton excitations of bosonic Laughlin $ν=1/2$ fractional quantum Hall (FQH) states on the torus and of their analog on the lattice, the fractional Chern insulators (FCIs). We show that, by applying the appropriate mapping of momentum quantum numbers between the two systems, the magneto-roton mode can be identified in FCIs and that it contains the same number of states as in the FQH case. Further, we numerically test the single mode approximation to the magneto-roton mode for both the FQH and FCI case. This proves particularly challenging for the FCI, because its eigenstates have a lower translational symmetry than the FQH states. In spite of this, we construct the FCI single-mode approximation such that it carries the same momenta as the FQH states, allowing for a direct comparison between the two systems. We show that the single-mode approximation captures well a dispersive subset of the magneto-roton excitations both for the FQH and the FCI case. We find remarkable quantitative agreement between the two systems. For example, the many-body excitation gap extrapolates to almost the same value in the thermodynamic limit.

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