FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS) |
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Higher-Order Topological Spin Hall Effect of Sound |
Zhi-Kang Lin1, Shi-Qiao Wu1, Hai-Xiao Wang2*, and Jian-Hua Jiang1* |
1School of Physical Science and Technology, and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006, China 2School of Physical Science and Technology, Guangxi Normal University, Guilin 541004, China
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Cite this article: |
Zhi-Kang Lin, Shi-Qiao Wu, Hai-Xiao Wang et al 2020 Chin. Phys. Lett. 37 074302 |
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Abstract We theoretically propose a reconfigurable two-dimensional (2D) hexagonal sonic crystal with higher-order topology protected by the six-fold, $C_{6}$, rotation symmetry. The acoustic band gap and band topology can be controlled by rotating the triangular scatterers in each unit cell. In the nontrivial phase, the sonic crystal realizes the topological spin Hall effect in a higher-order fashion: (i) the edge states emerging in the bulk band gap exhibit partial spin-momentum correlation and are gapped due to the reduced spatial symmetry at the edges. (ii) The gapped edge states, on the other hand, stabilize the topological corner states emerging in the edge band gap. The partial spin-momentum correlation is manifested as pseudo-spin-polarization of edge states away from the time-reversal invariant momenta, where the pseudospin is emulated by the acoustic orbital angular momentum. We reveal the underlying topological mechanism using a corner topological index based on the symmetry representation of the acoustic Bloch bands.
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Received: 28 April 2020
Published: 21 June 2020
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PACS: |
43.40.+s
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(Structural acoustics and vibration)
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43.20.+g
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(General linear acoustics)
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46.40.-f
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(Vibrations and mechanical waves)
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46.40.Cd
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(Mechanical wave propagation (including diffraction, scattering, and dispersion))
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Fund: Supported by the National Natural Science Foundation of China (Grant Nos. 11675116 and 11904060), the Jiangsu Distinguished Professor Fund, and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD). |
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