Diagnosing Floquet Chern and anomalous topological insulators based on Bloch oscillations

TL;DR

This paper proposes a hybrid waveguide array setup to distinguish Floquet Chern insulators from Floquet anomalous topological insulators by analyzing their unique Bloch oscillation behaviors, providing a clear bulk diagnostic method.

Contribution

It introduces a novel hybrid waveguide design and demonstrates how to diagnose Floquet topological phases through bulk Bloch oscillations, advancing topological phase identification techniques.

Findings

Bloch oscillations differ distinctly between FCI and FATI.

The proposed setup enables unambiguous bulk phase diagnosis.

Wavepacket dynamics reveal phase-specific displacement behaviors.

Abstract

It is challenging to distinguish Floquet Chern insulator (FCI) and Floquet anomalous topological insulator (FATI) because of their common features of chiral edge states and far away from equilibrium. A hybrid straight-curved waveguide array is proposed to enable topological phase transitions from FCI to FATI and show how to diagnose the two phases using Bloch oscillations. As a proof of principle, the hybrid straight-curved waveguide array is designed as a straight honeycomb waveguide array nested in an asynchronous curved Kagome waveguide array. Under a two-dimensional (2D) tilted potential created by the spatial gradient of refractive indices, an initial Gaussian-like wavepacket undergoes 2D Bloch oscillations, displaying quasi-quantized displacement in the FCI and no drift in the FATI. This approach offers a direct and unambiguous method to diagnose Floquet topological phases from the bulk response.