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Synthetic gauge flux and Weyl points in acoustic systems

Abstract

Following the discovery of the quantum Hall effect1,2 and topological insulators3,4, the topological properties of classical waves began to draw attention5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21. Topologically non-trivial bands characterized by non-zero Chern numbers are realized through either the breaking of time-reversal symmetry using an external magnetic field5,6,7,15,16 or dynamic modulation8,17. Owing to the absence of a Faraday-like effect, the breaking of time-reversal symmetry in an acoustic system is commonly realized with moving background fluids20,22, which drastically increases the engineering complexity. Here we show that we can realize effective inversion symmetry breaking and create an effective gauge flux in a reduced two-dimensional system by engineering interlayer couplings, achieving an acoustic analogue of the topological Haldane model2,23. We show that the synthetic gauge flux is closely related to Weyl points24,25,26 in the three-dimensional band structure and the system supports chiral edge states for fixed values of kz.

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Figure 1: Interlayer coupling induces different symmetry breakings in two-dimensional systems.
Figure 2: Different interlayer coupling coefficients induce effective breaking of in-plane inversion symmetry.
Figure 3: Chiral interlayer coupling induces a synthetic gauge flux.
Figure 4: Weyl points in the reciprocal space.

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Acknowledgements

The authors would like to thank Z. Q. Zhang and K. T. Law for discussions. This work was supported by the Hong Kong Research Grants Council (grant no. AoE/P-02/12).

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C.T.C. initiated the programme. M.X. and W.-J.C. contributed equally to this work. All authors contributed to the analysis and discussion of the results.

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Correspondence to C. T. Chan.

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The authors declare no competing financial interests.

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Xiao, M., Chen, WJ., He, WY. et al. Synthetic gauge flux and Weyl points in acoustic systems. Nature Phys 11, 920–924 (2015). https://doi.org/10.1038/nphys3458

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