Anomalous Topological Phases and Unpaired Dirac Cones in Photonic Floquet Topological Insulators

TL;DR

This paper introduces a new class of photonic Floquet topological insulators with tunable topological phases, unpaired Dirac cones, and controllable gauge fields, leading to novel transport phenomena and improved wave-guiding capabilities.

Contribution

It presents a novel design of photonic Floquet topological insulators with tunable topological transitions and unpaired Dirac cones, along with an efficient method for calculating their bandstructure.

Findings

Support for anomalous Floquet topological phases with zero Chern number

Presence of unpaired Dirac cones at topological transition points

Control of gauge field strength via lattice parameters

Abstract

We propose a class of photonic Floquet topological insulators based on staggered helical lattices and an efficient numerical method for calculating their Floquet bandstructure. The lattices support anomalous Floquet topological insulator phases with vanishing Chern number and tunable topological transitions. At the critical point of the topological transition, the bandstructure hosts a single unpaired Dirac cone, which yields a variety of unusual transport effects: a discrete analogue of conical diffraction, weak antilocalization not limited by intervalley scattering, and suppression of Anderson localization. Unlike previous designs, the effective gauge field strength can be controlled via lattice parameters such as the inter-helix distance, significantly reducing radiative losses and enabling applications such as switchable topological wave-guiding.