Three-dimensional higher-order topological acoustic system with multidimensional topological states

Abstract

Topologically protected gapless edge/surface states are phases of quantum matter which behave as massless Dirac fermions, immunizing against disorders and continuous perturbations. Recently, a new class of topological insulators (TIs) with gapped edge states and in-gap corner states have been theoretically predicted in electric systems 1,2, and experimentally realized in two-dimensional (2D) mechanical and electromagnetic systems 3,4, electrical circuits 5, optical and sonic crystals 6-11, and elastic phononic plates 12. Here, we elaborately design a strong three-dimensional (3D) topological acoustic system, by arranging acoustic meta-atoms in a simple cubic lattice. Under the direct field measurements, besides of the 2D surface propagations on all of the six surfaces, the 1D hinge propagations behaving as robust acoustic fibers along the twelve hinges and the 0D corner modes working as robust localized resonances at the eight corners are experimentally confirmed. As these multidimensional topological states are activated in different frequencies and independent spaces, our works pave feasible ways for applications in the topological acoustic cavities, communications and signal-processing.

23 pages,6 figures

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Cited by in corpus (9)

• Classical higher-order topological insulators
• Topological acoustics
• Topological photonic crystals: physics, designs and applications
• Higher-order topological phases in crystalline and non-crystalline systems: a review
• Realization of Surface-Obstructed Topological Insulators
• Microwave hinge states in a simple-cubic-lattice photonic crystal insulator
• Edge States with Hidden Topology in Spinner Lattices
• Nonlinearity-induced corner states in a kagome lattice
• Three-dimensional higher-order topological insulator protected by cubic symmetry