Mechanically‐Reconfigurable Edge States in an Ultrathin Valley‐Hall Topological Metamaterial

Abstract

Broadband topological metamaterials hold the key for designing the next generation of integrated photonic platforms and microwave devices given their protected back‐scattering‐free and unidirectional edge states, among other exotic properties. However, synthesizing such metamaterial has proven challenging. Here, a broadband bandgap (relative bandwidth of more than 43%) Valley‐Hall topological metamaterial with deep subwavelength thickness is proposed. The present topological metamaterial is composed of three layers printed circuit boards whose total thickness is 1.524 mm ≈ λ/100. The topological phase transition is achieved by introducing an asymmetry parameter δr. Three mechanically reconfigurable edge states can be obtained by varying interlayer displacement. Their robust transmission is demonstrated through two kinds of waveguide domain walls with cavities and disorders. Exploiting the proposed topological metamaterial, a six‐way power divider is constructed and measured as a proof‐of‐concept of the potential of the proposed technology for future electromagnetic devices.

Evolution of the edge states and corner states in a multilayer honeycomb valley-Hall topological metamaterial

“…We construct AB-type or BA-type domain walls by using structure A and structure B, and the two domain walls will lead to a pair of topological kink edge states around the K/K valley. Since the variation of VCN on the domain wall is related to the existence of backpropagation edge states, the pair of kinking edge states is restricted to different valleys, and their propagation directions along the interface are completely opposite, showing "valley-lock" chirality [34][35][36][37][38][39][40]. As shown in Figs.…”

“…The topological corner states can be selectively switched, which provides a fundamental understanding of the interaction between higher-order topology and the valley degrees of freedom. In our previous work, we have also achieved an edge state with a gapped region in mechanically reconfigurable valley-Hall topological metamaterials [38]. Although great achievements have been made in topological edge states and corner states, it is still a challenge to achieve the evolvement rule of the different edge states from the conventional crossed edge state to the fully gapped edge state.…”