Topological Surface States in a Gyroid Acoustic Crystal

Area of Science:

• Acoustics
• Condensed Matter Physics
• Materials Science

Background:

• Acoustic crystals offer tunable wave manipulation properties.
• Topological phononics explores wave phenomena in materials with non-trivial band topology.
• Gyroid structures, derived from minimal surfaces, exhibit unique symmetries and properties.

Purpose of the Study:

• To investigate the acoustic properties of gyroid-based acoustic crystals.
• To explore the emergence of topological degeneracies and surface states in these materials.
• To demonstrate the potential of gyroid acoustic crystals for novel acoustic applications.

Main Methods:

• Numerical simulations of acoustic wave propagation in gyroid structures.
• Analysis of band structures to identify topological features like Weyl and Dirac points.
• Experimental validation using additively manufactured samples.

Main Results:

• Identification of spin-1 Weyl and charge-2 Dirac degenerate points enforced by nonsymmorphic symmetry.
• Observation of multi-fold topological degeneracies arising naturally from gyroid geometry.
• Experimental validation of chiral surface states with open arcs and negative refraction.

Conclusions:

• Gyroid acoustic crystals exhibit non-trivial topology leading to unique surface states.
• These materials demonstrate potential for directional wave confinement and negative refraction.
• The findings suggest gyroid phononic materials as effective building blocks for advanced acoustic applications, including soundproofing and structural components.