Vortex states in an acoustic Weyl crystal with a topological lattice defect

TL;DR

This paper demonstrates the design and experimental realization of a three-dimensional acoustic Weyl metamaterial that hosts topologically protected vortex modes bound to a lattice defect, enabling robust waveguiding and vortex emission.

Contribution

It introduces a novel 3D acoustic Weyl crystal with topological defect-bound modes, linking bulk band topology to defect-bound states and their unique properties.

Findings

Robust topological vortex modes observed in experiments.

Modes exhibit orbital angular momentum locked to propagation.

Potential for new topological acoustic device applications.

Abstract

We design and implement a three dimensional acoustic Weyl metamaterial hosting robust modes bound to a one-dimensional topological lattice defect. The modes are related to topological features of the bulk bands, and carry nonzero orbital angular momentum locked to the direction of propagation. They span a range of axial wavenumbers defined by the projections of two bulk Weyl points to a one-dimensional subspace, in a manner analogous to the formation of Fermi arc surface states. We use acoustic experiments to probe their dispersion relation, orbital angular momentum locked waveguiding, and ability to emit acoustic vortices into free space. These results point to new possibilities for creating and exploiting topological modes in three-dimensional structures through the interplay between band topology in momentum space and topological lattice defects in real space.