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Title: Observation of an acoustic octupole topological insulator
Authors: Xue, Haoran
Ge, Yong
Sun, Hong-Xiang
Wang, Qiang
Jia, Ding
Guan, Yi-Jun
Yuan, Shou-Qi
Chong, Yidong
Zhang, Baile
Keywords: Science::Physics
Issue Date: 2020
Source: Xue, H., Ge, Y., Sun, H., Wang, Q., Jia, D., Guan, Y., Yuan, S., Chong, Y. & Zhang, B. (2020). Observation of an acoustic octupole topological insulator. Nature Communications, 11(1), 2442-.
Project: MOE2018-T2-1-022 (S)
Journal: Nature Communications
Abstract: Berry phase associated with energy bands in crystals can lead to quantised observables like quantised dipole polarizations in one-dimensional topological insulators. Recent theories have generalised the concept of quantised dipoles to multipoles, resulting in the discovery of multipole topological insulators which exhibit a hierarchy of multipole topology: a quantised octupole moment in a three-dimensional bulk induces quantised quadrupole moments on its two-dimensional surfaces, which in turn induce quantised dipole moments on one-dimensional hinges. Here, we report on the realisation of an octupole topological insulator in a three-dimensional acoustic metamaterial. We observe zero-dimensional topological corner states, one-dimensional gapped hinge states, two-dimensional gapped surface states, and three-dimensional gapped bulk states, representing the hierarchy of octupole, quadrupole and dipole moments. Conditions for forming a nontrivial octupole moment are demonstrated by comparisons with two different lattice configurations having trivial octupole moments. Our work establishes the multipole topology and its full hierarchy in three-dimensional geometries.
ISSN: 2041-1723
DOI: 10.1038/s41467-020-16350-1
DOI (Related Dataset): 10.21979/N9/94CPSE
Schools: School of Physical and Mathematical Sciences 
Research Centres: Centre for Disruptive Photonic Technologies (CDPT) 
Rights: © 2020 The Author(s). This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit licenses/by/4.0/.
Fulltext Permission: open
Fulltext Availability: With Fulltext
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