Engineering Higher-Order Topological Confinement via Acoustic Non-Hermitian Textures.

Area of Science:

• Condensed matter physics
• Acoustic metamaterials
• Topological physics

Background:

• Higher-order topological insulators exhibit unique boundary states like hinge or corner states.
• Non-Hermitian topological properties emerge with the inclusion of gain or loss, offering richer phenomena.
• Implementing gain in topological systems presents significant experimental challenges.

Purpose of the Study:

• To construct and demonstrate a non-Hermitian second-order topological insulator (SOTI) using acoustic waves.
• To investigate the effects of engineered gain and loss on topological properties in a cavity-based lattice.
• To explore the design of unconventional topological states through flexible control of non-Hermitian responses.

Main Methods:

• A cavity-based lattice was designed to exhibit non-Hermitian properties.
• Electro-thermoacoustic gain and loss were introduced into the lattice.
• Electrically biased carbon nanotube films were used to precisely control the spatial distribution and strength of gain and loss.

Main Results:

• The experimental setup successfully demonstrated a non-Hermitian second-order topological insulator.
• Flexible engineering of gain and loss textures allowed for the creation of unconventional interface and corner confining topologies.
• The ability to manipulate non-Hermitian responses at will was confirmed.

Conclusions:

• The developed acoustic SOTI provides a versatile platform for studying non-Hermitian topology.
• This work opens new avenues for designing novel topological states with tailored properties.
• Potential applications include energy harvesting and advancing fundamental understanding in topological physics.