Topological dislocation modes in three-dimensional acoustic topological insulators

TL;DR

This paper provides the first clear experimental evidence of bulk-dislocation correspondence in a three-dimensional acoustic topological insulator by directly measuring gapless dislocation modes, demonstrating their unidirectional guidance along arbitrary paths.

Contribution

It introduces a controllable 3D acoustic topological insulator system that unambiguously demonstrates bulk-dislocation correspondence with measurable topological dislocation modes.

Findings

Direct measurement of gapless dislocation modes in 3D acoustic insulators

Unidirectional guidance of dislocation modes along arbitrary paths

Potential for topological wave control in classical systems

Abstract

Dislocations are ubiquitous in three-dimensional solid-state materials. The interplay of such real space topology with the emergent band topology defined in reciprocal space gives rise to gapless helical modes bound to the line defects. This is known as bulk-dislocation correspondence, in contrast to the conventional bulk-boundary correspondence featuring topological states at boundaries. However, to date rare compelling experimental evidences are presented for this intriguing topological observable, owing to the presence of various challenges in solid-state systems. Here, using a three-dimensional acoustic topological insulator with precisely controllable dislocations, we report an unambiguous experimental evidence for the long-desired bulk-dislocation correspondence, through directly measuring the gapless dispersion of the one-dimensional topological dislocation modes. Remarkably, as revealed in our further experiments, the pseudospin-locked dislocation modes can be unidirectionally guided in an arbitrarily-shaped dislocation path. The peculiar topological dislocation transport, expected in a variety of classical wave systems, can provide unprecedented controllability over wave propagations.