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Title: Acoustic higher-order topological insulator on a kagome lattice
Authors: Xue, Haoran
Yang, Yahui
Gao, Fei
Chong, Yidong
Zhang, Baile
Keywords: Science::Physics
Issue Date: 2019
Source: Xue, H., Yang, Y., Gao, F., Chong, Y., & Zhang, B. (2019). Acoustic higher-order topological insulator on a kagome lattice. Nature Materials, 18(2), 108-112. doi:10.1038/s41563-018-0251-x
Journal: Nature Materials
Abstract: Higher-order topological insulators1-5 are a family of recently predicted topological phases of matter that obey an extended topological bulk-boundary correspondence principle. For example, a two-dimensional (2D) second-order topological insulator does not exhibit gapless one-dimensional (1D) topological edge states, like a standard 2D topological insulator, but instead has topologically protected zero-dimensional (0D) corner states. The first prediction of a second-order topological insulator1, based on quantized quadrupole polarization, was demonstrated in classical mechanical6 and electromagnetic7,8 metamaterials. Here we experimentally realize a second-order topological insulator in an acoustic metamaterial, based on a 'breathing' kagome lattice9 that has zero quadrupole polarization but a non-trivial bulk topology characterized by quantized Wannier centres2,9,10. Unlike previous higher-order topological insulator realizations, the corner states depend not only on the bulk topology but also on the corner shape; we show experimentally that they exist at acute-angled corners of the kagome lattice, but not at obtuse-angled corners. This shape dependence allows corner states to act as topologically protected but reconfigurable local resonances.
ISSN: 1476-1122
DOI: 10.1038/s41563-018-0251-x
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:SPMS Journal Articles

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