One-Dimensional Z_{2} Topological Skin Effect Driven by Acoustic Lossy Couplings

Area of Science:

• Condensed Matter Physics
• Acoustics
• Metamaterials

Background:

• The non-Hermitian skin effect (NHSE) is a phenomenon where bulk states localize at boundaries.
• The non-Bloch framework and generalized Brillouin zone characterize NHSE in 1D systems.
• NHSE is classified into Z and Z2 types based on current functional properties.

Purpose of the Study:

• To experimentally demonstrate a 1D Z2 non-Hermitian skin effect (NHSE) in a passive acoustic system.
• To establish a platform for observing spin-polarized skin localization.
• To explore spin-momentum locked wave control in non-Hermitian topological metamaterials.

Main Methods:

• Utilized a bilayer sonic crystal with tailored lossy couplings.
• Introduced an artificial gauge field via staggered interlayer couplings.
• Implemented tunable dissipation using sound-absorbing sponges.

Main Results:

• Successfully demonstrated the 1D Z2 NHSE in a passive acoustic system.
• Observed spin-polarized skin localization with spin-up and spin-down states accumulating at opposite ends.
• Confirmed the effect through band dispersion, spatial field mapping, and transmission spectroscopy.

Conclusions:

• Presented the first purely passive platform for Z2 NHSE in acoustics.
• Opened avenues for spin-momentum locked wave control in non-Hermitian topological metamaterials.
• This work provides a new system for studying topological phenomena in acoustics.