Limits of topological protection under local periodic driving

TL;DR

This paper investigates how local periodic driving affects topological edge states in Floquet systems, revealing that dynamic perturbations can cause edge state depopulation despite static topological protection.

Contribution

The study demonstrates the limits of topological protection under local periodic driving using experimental quantum simulators and Floquet analysis.

Findings

Local periodic driving can depopulate topological edge states.

Coupling of Floquet replicas to bulk bands causes edge state decay.

Experimental and numerical results agree on depopulation mechanisms.

Abstract

The bulk-edge correspondence guarantees that the interface between two topologically distinct insulators supports at least one topological edge state that is robust against static perturbations. Here, we address the question of how dynamic perturbations of the interface affect the robustness of edge states. We illuminate the limits of topological protection for Floquet systems in the special case of a static bulk. We use two independent dynamic quantum simulators based on coupled plasmonic and dielectric photonic waveguides to implement the topological Su-Schriefer-Heeger model with convenient control of the full space- and time-dependence of the Hamiltonian. Local time periodic driving of the interface does not change the topological character of the system but nonetheless leads to dramatic changes of the edge state, which becomes rapidly depopulated in a certain frequency window. A theoretical Floquet analysis shows that the coupling of Floquet replicas to the bulk bands is responsible for this effect. Additionally, we determine the depopulation rate of the edge state and compare it to numerical simulations.