Antihelical Edge States in Two-dimensional Photonic Topological Metals

TL;DR

This paper introduces antihelical edge states in topological metals, demonstrating their robust propagation in photonic lattices and their transition to helical states in insulating phases, opening new avenues in topological photonics.

Contribution

It proposes a novel class of antihelical edge states in topological metals and their photonic realization, expanding the understanding of topological edge phenomena.

Findings

Antihelical edge states propagate robustly across lattice corners.

Transition from antihelical to helical edge states occurs during a metal-insulator phase change.

Potential applications in topologically-protected light transport and photonic devices.

Abstract

Topological edge states are the core of topological photonics. Here we introduce the antihelical edge states of time-reversal symmetric topological metals and propose a photonic realization in an anisotropic square lattice of coupled ring resonators, where the clockwise and counterclockwise modes play the role of pseudospins. The antihelical edge states robustly propagate across the corners toward the diagonal of the square lattice: The same (opposite) pseudospins copropagate in the same (opposite) direction on the parallel lattice boundaries; the different pseudospins separate and converge at the opposite corners. The antihelical edge states in the topological metallic phase alter to the helical edge states in the topological insulating phase under a metal-insulator phase transition. The antihelical edge states provide a unique manner of topologically-protected robust light transport applicable for topological purification. Our findings create new opportunities for topological photonics and metamaterials.