Dislocation as a bulk probe of higher-order topological insulators

Bitan Roy, Vladimir Juricic

Published 2020-06-08Version 1

Topological materials occupy the central stage in the modern condensed matter physics because of their robust metallic edge or surface states protected by the topological invariant, characterizing the electronic band structure in the bulk. Higher order topological (HOT) states extend this usual bulk-boundary correspondence, so they host the modes localized at lower-dimensional boundaries, such as corners and hinges, which may hinder their experimental detection. Here, we theoretically demonstrate that dislocations, ubiquitous defects in crystalline materials, can probe higher-order topology, recently realized in various platforms, such as crystalline, phononic, photonic, topoeletric, and artificial lattice systems. As we show, HOT insulators respond to a dislocation defect through the protected finite-energy in-gap modes, localized at the defect core in the bulk of a second-order topological insulator. Our findings are consequential for the systematic probing of the extended bulk-boundary correspondence in a broad range of HOT crystals and metamaterials through the bulk topological lattice defects, controllable in state-of-the-art experiments.