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Acoustic higher-order topological insulator on a kagome lattice

Acoustic higher-order topological insulator on a kagome lattice Higher-order topological insulators 1–5 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 insulator 1 , based on quantized quadrupole polarization, was demonstrated in classical mechanical 6 and electromagnetic 7,8 metamaterials. Here we experimentally realize a second-order topological insulator in an acoustic metamaterial, based on a ‘breathing’ kagome lattice 9 that has zero quadrupole polarization but a non-trivial bulk topology characterized by quantized Wannier centres 2,9,10 . 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. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Nature Materials Springer Journals

Acoustic higher-order topological insulator on a kagome lattice

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References (37)

Publisher
Springer Journals
Copyright
Copyright © 2018 by The Author(s), under exclusive licence to Springer Nature Limited
Subject
Materials Science; Materials Science, general; Optical and Electronic Materials; Biomaterials; Nanotechnology; Condensed Matter Physics
ISSN
1476-1122
eISSN
1476-4660
DOI
10.1038/s41563-018-0251-x
Publisher site
See Article on Publisher Site

Abstract

Higher-order topological insulators 1–5 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 insulator 1 , based on quantized quadrupole polarization, was demonstrated in classical mechanical 6 and electromagnetic 7,8 metamaterials. Here we experimentally realize a second-order topological insulator in an acoustic metamaterial, based on a ‘breathing’ kagome lattice 9 that has zero quadrupole polarization but a non-trivial bulk topology characterized by quantized Wannier centres 2,9,10 . 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.

Journal

Nature MaterialsSpringer Journals

Published: Dec 31, 2018

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