Trapped state at a dislocation in a weak magnetomechanical topological insulator

TL;DR

This paper experimentally demonstrates a 2D weak topological insulator in a magneto-mechanical metamaterial, revealing anisotropic edge modes and a bound state at a dislocation, highlighting unique properties of WTIs.

Contribution

The study constructs and experimentally verifies a 2D WTI using magneto-mechanical metamaterials, showcasing its anisotropic edge modes and dislocation-bound states.

Findings

2D WTI exhibits anisotropic edge modes

Bound state observed at dislocation defect

Constructed from stacked 1D SSH chains

Abstract

Topological insulators (TIs) are characterized by an insulating bulk and symmetry protected bound state on their boundaries. A "strong" topological insulator is characterized by robust conducting states on \emph{all} boundaries protected by certain internal symmetries. A "weak" topological insulator (WTI) however, requires lattice translation symmetry, making it more sensitive to disorder. However, this sensitivity gives rise to interesting characteristics such as anisotropic edge modes, quantized charge polarization, and bound states appearing at dislocation defects. Despite hosting interesting features, the sensitivity of WTIs to disorder poses an experimental confirmation challenge. Here we realize a 2D magneto-mechanical metamaterial and demonstrate experimentally the unique features of a WTI. Specifically, we show that the 2D WTI is anisotropic and hosts edge modes only on certain edges, as well as hosting a bound state at a dislocation defect. We construct the 2D WTI from stacked 1D SSH chains for which we show experimentally the different gapped phases of the 1D model.