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Topological acoustics

Abstract

Topological acoustics is an emerging field that lies at the intersection of condensed matter physics, mechanical structural design and acoustics engineering. It explores the design and construction of novel artificial structures, such as acoustic metamaterials and phononic crystals, to manipulate sound waves robustly, taking advantage of topological protection. Early work on topological acoustics was limited to duplicating topological phases that have been understood in condensed matter systems, but recent advances have shifted to exploring new topological concepts that are difficult to realize in other physical systems, such as various topological semimetal phases, and topological phases associated with Floquet engineering, fragile topology, non-Hermiticity and synthetic dimensions. These developments demonstrate the unique advantages of topological acoustic systems and their role in developing topological physics. In this Review, we survey the fundamental mechanisms, basic designs and practical realizations of topological phases in acoustic systems and provide an overview of future directions and potential applications.

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Fig. 1: Summary of different types of topological phase.
Fig. 2: Acoustic analogues of 2D topological insulating phases.
Fig. 3: Acoustic topological phases with quantized dipole and multipole moments.
Fig. 4: Acoustic Weyl crystals.
Fig. 5: Acoustic topological semimetals beyond conventional Weyl phases.
Fig. 6: Novel acoustic topological phases.

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Acknowledgements

H.X. and B.Z. acknowledge support from National Research Foundation Singapore Competitive Research Program no. NRF-CRP23-2019-0007, and Singapore Ministry of Education Academic Research Fund Tier 3 under grant no. MOE2016-T3-1-006 and Tier 2 under grant no. MOE2019-T2-2-085. Y.Y. acknowledges support from the National Natural Science Foundation of China (NNSFC) under grant no. 62175215.

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Xue, H., Yang, Y. & Zhang, B. Topological acoustics. Nat Rev Mater 7, 974–990 (2022). https://doi.org/10.1038/s41578-022-00465-6

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