Topological transition of Dirac points in a microwave experiment

TL;DR

This study demonstrates a topological transition in a microwave analogue of a graphene-like lattice, revealing how anisotropy induces a phase change and edge-localized states at the Dirac point.

Contribution

It experimentally shows a topological transition in a microwave system and maps edge-localized states associated with the Dirac points.

Findings

Observation of a transition from gapless to gapped phases

Mapping of wave functions showing edge localization

Controlled anisotropy induces topological phase change

Abstract

By means of a microwave tight-binding analogue experiment of a graphene-like lattice, we observe a topological transition between a phase with a point-like band gap characteristic of massless Dirac fermions and a gapped phase. By applying a controlled anisotropy on the structure, we investigate the transition directly via density of states measurements. The wave function associated with each eigenvalue is mapped and reveals new states at the Dirac point, localized on the armchair edges. We find that with increasing anisotropy, these new states are more and more localized at the edges.