Higher-order topological phases in tunable $C_3$-symmetric photonic crystals

TL;DR

This paper explores how changing the geometry of kagome photonic crystals induces higher-order topological phases, revealing multiple transitions and topological states with potential for experimental realization.

Contribution

It demonstrates tunable higher-order topological transitions in photonic crystals using a single geometric parameter, identifying distinct topological phases and introducing a photonic fractional corner charge analog.

Findings

Multiple higher-order topological transitions achieved by geometry tuning.

Identification of two distinct higher-order topological insulator phases.

Introduction of a photonic fractional corner charge concept.

Abstract

We demonstrate that multiple higher-order topological transitions can be triggered via the continuous change of the geometry in kagome photonic crystals composed of three dielectric rods. By tuning a single geometry parameter, the photonic corner and edge states emerge or disappear with the higher-order topological transitions. Two distinct higher-order topological insulator phases and a normal insulator phase are revealed. Their topological indices are obtained from symmetry representations. A photonic analog of fractional corner charge is introduced to distinguish the two higher-order topological insulator phases. Our predictions can be readily realized and verified in configurable dielectric photonic crystals.