Synthetic gauge field and pseudospin-orbit interaction in a stacked two-dimensional ring-network lattice

TL;DR

This paper explores how synthetic gauge fields and pseudospin-orbit interactions influence topological phases in a stacked 2D ring-network model, revealing complex spectral features and phase transitions relevant for photonic systems.

Contribution

It introduces a bosonic model simulating light propagation that incorporates synthetic gauge fields and pseudospin-orbit interactions, analyzing their effects on topological phases.

Findings

Synthetic magnetic field creates a Hofstadter-butterfly spectrum.

Pseudospin-orbit interaction destroys Floquet-topological-insulator phases.

Breaking space-inversion symmetry preserves Floquet-Weyl phases with Weyl points.

Abstract

We study the effects of a synthetic gauge field and pseudospin-orbit interaction in a stacked two-dimensional ring-network model. The model was introduced to simulate light propagation in the corresponding ring-resonator lattice, and is thus completely bosonic. Without these two items, the model exhibits Floquet-Weyl and Floquet-topological-insulator phases with topologically gapless and gapped band structures, respectively. The synthetic magnetic field implemented in the model results in a three-dimensional Hofstadter-butterfly-type spectrum in a photonic platform. The resulting gaps are characterization by the winding number of relevant S-matrices together with the Chern number of the bulk bands. The pseudospin-orbit interaction is defined as the mixing term between two pseudospin degrees of freedom in the rings, namely, the clockwise and counter-clockwise modes. It destroys the Floquet-topological-insulator phases, while the Floquet-Weyl phase with multiple Weyl points can be preserved by breaking the space-inversion symmetry. Implementing both the synthetic gauge field and pseudospin-orbit interaction requires a certain nonreciprocity.