Higher-order topological phase induced by hybrid magneto-electric resonances

TL;DR

This paper introduces a novel method to engineer higher-order topological phases in photonics by exploiting the dual electric and magnetic responses of meta-atoms, enabling reconfigurable topological states through particle alignment.

Contribution

It presents a new mechanism for topological phase control in photonics using hybrid magneto-electric resonances, unlike previous lattice geometry-based approaches.

Findings

Demonstrated topological edge and corner states in microwave experiments.

Showed tunability of topological phases via meta-atom orientation.

Provided a flexible reconfiguration method for topological photonic states.

Abstract

Rapid development of topological concepts in photonics unveils exotic phenomena such as unidirectional propagation of electromagnetic waves resilient to backscattering at sharp bends and disorder-immune localization of light at stable frequencies. Recently introduced higher-order topological insulators (HOTIs) bring in additional degrees of control over light confinement and steering. However, designs of photonic HOTIs reported so far are solely exploiting lattice geometries which are hard to reconfigure thus limiting tunability. Here, we elaborate a conceptually new mechanism to engineer higher-order topological phases which relies on the dual nature of electromagnetic field and exploits both electric and magnetic responses of the meta-atoms. Hybridization between these responses gives rise to the difference in the effective coupling which is controlled by the meta-atoms mutual orientations. This feature facilitates us to tailor photonic band topology exclusively via particle alignment and to flexibly reconfigure the topological phase. Focusing on the kagome array of split-ring resonators, we experimentally demonstrate topological edge and corner states in the microwave domain. Our findings provide a new promising route to induce and control higher-order topological phases and states.