Diagnosing Floquet Chern and anomalous topological insulators based on Bloch oscillations

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.