Observation of disorder-induced boundary localization

Area of Science:

• Condensed Matter Physics
• Wave Phenomena
• Topological Physics

Background:

• Anderson localization describes wave function localization in disordered systems.
• Topology in physics reveals robust phenomena, including topological insulators.
• Non-Hermitian systems exhibit unique topological features like point-gap topology and the non-Hermitian skin effect.

Purpose of the Study:

• To experimentally demonstrate disorder-induced point-gap topology in a non-Hermitian acoustic crystal.
• To investigate the influence of disorder on the non-Hermitian skin effect.
• To explore novel localization phenomena beyond conventional Anderson localization.

Main Methods:

• Fabrication of a non-Hermitian acoustic crystal with engineered disorder.
• Experimental characterization of wave propagation and eigenstate localization.
• Systematic variation of disorder strength and coupling types (nearest-neighbor and next-nearest-neighbor).

Main Results:

• Demonstrated disorder-induced point-gap topology and the non-Hermitian skin effect.
• Observed reversal of boundary localization direction with increasing disorder strength.
• Observed a 'bipolar' skin effect with localization at both boundaries for next-nearest-neighbor disorder.

Conclusions:

• Disorder can induce unique topological phenomena in non-Hermitian systems.
• The non-Hermitian skin effect exhibits tunable boundary localization controlled by disorder.
• These findings reveal a new mechanism for disorder-induced localization in non-Hermitian systems.