Teaching sound topological tricks

The concept of topological phases have not only revolutionized our understanding of physics or materials, but also brought about new possibilities for applications. Recent advances in higher-order topological insulators show that multiple forms of topological states can exist at boundaries of different dimensions, which greatly enriched the potentials for diverse applications. Interesting, the topological phases can also be implemented in artificial structures in photonics, electromagnetism, and acoustics.

A recent work co-led by Dr. Guancong Ma from Hong Kong Baptist University and Dr. Ying Wu from King Abdullah University of Science and Technology explored the controlling sound propagation with topological modes at different dimensions. They designed and built a phononic crystal that hosts robust topological states at three different dimensions, i.e., 2D topological surface states, 1D topological hinge states, and 0D topological corner states. The researchers showed that these different topological states can be used for different kinds of wave steering. The 2D topological surface states can be engineered to realize negative refraction of sound wave. And the 1D topological hinge states are used as transport channels much like waveguides that can bend in all three spatial directions. An acoustic interferometer is realized leveraging this characteristics. This work showcases that topological states can be tailored for wave steering applications across multiple dimensions.

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This work was supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. OSR-2016-CRG5-2950 and KAUST Baseline Research Fund BAS/1/1626-01-01. This work was also supported by Hong Kong Research Grants Council (12302420, 12300419, 22302718, C6013-18G), the National Natural Science Foundation of China via the Excellent Young Scientist Scheme (Hong Kong & Macao) (11922416) and the Youth Program (11802256), and Hong Kong Baptist University (RC-SGT2/18-19/SCI/006).

See the article:

Changqing Xu, Ze-Guo Chen, Guanqing Zhang, Guancong Ma, Ying Wu, Multi-dimensional wave steering with higher-order topological phononic crystal, Science Bulletin, 2021, DOI: 10.1016/j.scib.2021.05.013

https://www.sciencedirect.com/science/article/pii/S2095927321003509