The Nature of Topological Protection in Spin and Valley Hall Insulators

TL;DR

This paper uses group theory to analyze the topological protection in 2D dielectric photonic systems, providing design principles and understanding of backscattering limits for optical topological insulators.

Contribution

It offers a rigorous, group-theoretical framework to characterize and design topological photonic systems, clarifying the nature and limits of topological protection.

Findings

Identifies conditions for topological protection in dielectric photonic systems

Provides design principles for 2D hexagonal topological photonic structures

Clarifies the limits of backscattering immunity in these systems

Abstract

Recent interest in optical analogues to the quantum spin Hall and quantum valley Hall effects is driven by the promise to establish topologically protected photonic edge modes at telecommunication and optical wavelengths on a simple platform suitable for industrial applications. While first theoretical and experimental efforts have been made, these approaches so far both lack a rigorous understanding of the nature of topological protection and the limits of backscattering immunity. We here use a generic group theoretical methodology to fill this gap and obtain general design principles for purely dielectric two-dimensional topological photonic systems. The method comprehensively characterizes possible 2D hexagonal designs and reveals their topological nature, potential and limits.