Observation of photonic anomalous Floquet topological insulators.
Observation of photonic anomalous Floquet topological insulators.
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DOI：
10.1038/ncomms13756
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发表时间：
2017-01-04
影响因子：
16.6
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中科院分区：
文献类型：
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拓扑绝缘体是一类新型材料，由于拓扑保护，其沿其边缘表现出鲁棒性和无散射传输-独立于系统和边缘的精细细节。为了在没有额外对称性的情况下对二维系统的拓扑特征进行分类，人们通常使用陈氏数，因为从特定带隙以下的所有带中计算出的陈氏数之和等于穿过该带隙的手性边缘模式的净数量。然而，这仅在具有静态哈密顿量的情况下严格有效。陈氏数并没有给出周期驱动系统拓扑性质的完整表征。在我们的工作中，我们实现了一个虽然所有带的陈恩数为零但仍然存在手性边缘模式的系统。我们采用周期性驱动的光子波导晶格，并在这种异常Floquet拓扑绝缘体中证明了拓扑保护的无散射边缘输运。消失的陈氏数通常意味着系统在拓扑上是平凡的，但是对于周期性驱动的系统，这条规则可能被违反。在这里，Maczewsky等人报道了周期性驱动光子晶格中所有带的陈氏数为零的拓扑保护边缘模式。
Topological insulators are a new class of materials that exhibit robust and scatter-free transport along their edges — independently of the fine details of the system and of the edge — due to topological protection. To classify the topological character of two-dimensional systems without additional symmetries, one commonly uses Chern numbers, as their sum computed from all bands below a specific bandgap is equal to the net number of chiral edge modes traversing this gap. However, this is strictly valid only in settings with static Hamiltonians. The Chern numbers do not give a full characterization of the topological properties of periodically driven systems. In our work, we implement a system where chiral edge modes exist although the Chern numbers of all bands are zero. We employ periodically driven photonic waveguide lattices and demonstrate topologically protected scatter-free edge transport in such anomalous Floquet topological insulators. Vanishing Chern numbers usually mean that a system is topologically trivial, but this rule may be violated for periodically driven systems. Here, Maczewsky et al. report topologically protected edge modes in a periodically driven photonic lattice with all bands of zero Chern number.
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DOI：
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发表时间：
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影响因子：
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通讯作者：
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