Synthetic gauge fields and Weyl point in Time-Reversal Invariant Acoustic Systems

TL;DR

This paper demonstrates the creation of topological acoustic systems with synthetic gauge fields and Weyl points by structural engineering, enabling unidirectional edge states without magnetic fields.

Contribution

It introduces a novel method to realize effective gauge fields and inversion symmetry breaking in acoustic systems through structural design, mimicking the Haldane model.

Findings

Realization of topological edge states immune to backscattering.

Identification of Weyl points in the three-dimensional band structure.

Achievement of unidirectional wave propagation in acoustic systems.

Abstract

Inspired by the discovery of quantum hall effect and topological insulator, topological properties of classical waves start to draw worldwide attention. Topological non-trivial bands characterized by non-zero Chern numbers are realized with external magnetic field induced time reversal symmetry breaking or dynamic modulation. Due to the absence of Faraday-like effect, the breaking of time reversal symmetry in an acoustic system is commonly realized with moving background fluids, and hence drastically increases the engineering complexity. Here we show that we can realize effective inversion symmetry breaking and effective gauge field in a reduced two-dimensional system by structurally engineering interlayer couplings, achieving an acoustic analog of the topological Haldane model. We then find and demonstrate unidirectional backscattering immune edge states. We show that the synthetic gauge field is closely related to the Weyl points in the three-dimensional band structure.