Elastic Higher-Order Topological Insulator with Topologically Protected Corner States

Area of Science:

• Condensed Matter Physics
• Topological Materials
• Acoustics and Mechanics

Background:

• Topological phases, including higher-order topological insulators (HOTIs), offer robust control over wave propagation.
• HOTIs have been realized in various systems, but experimental demonstrations in continuous elastic media are emerging.

Purpose of the Study:

• To experimentally realize higher-order topological states in a 2D continuous elastic system.
• To investigate the properties and localization of topological edge and corner states in this system.

Main Methods:

• Fabrication and characterization of a 2D continuous elastic system.
• Experimental observation of gapped 1D edge states and 0D corner states.
• Analysis of topological protection and defect immunity of corner states.

Main Results:

• Observation of gapped 1D edge states and both trivial and topologically protected 0D corner states.
• Topological corner states are robustly localized at obtuse corners, unlike trivial modes.
• Demonstration of defect immunity for topological corner states.

Conclusions:

• Higher-order topological states are successfully realized in a 2D continuous elastic system.
• Topological corner states exhibit unique localization properties and defect immunity, dependent on corner geometry.
• This work opens avenues for designing reconfigurable topological acoustic and mechanical devices.