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Department of Physics

A new and experimentally feasible observable for anomalous Floquet topology

Spectrum of the periodically driven system showing the quasi-energy as a function of quasi-momentum with the bulk bands in grey and the chiral edge states in blue. The spectrum is periodic in energy and allows for edge states in the additional band gap. © Luca Asteria
Spectrum of the periodically driven system showing the quasi-energy as a function of quasi-momentum with the bulk bands in grey and the chiral edge states in blue. The spectrum is periodic in energy and allows for edge states in the additional band gap.
In a new article, we introduce a new and experimentally feasible observable for anomalous Floquet topology

In an international collaboration with Kyoto University, University of Hamburg and TU Berlin, we propose a new method to determine the presence of anomalous Floquet topology in periodically driven systems via a simple real-space bulk observable. Topology is an important concept in solid state physics and synthetic quantum systems connecting bulk topological indices to the presence of protected chiral states at the edge of the system. In periodically driven systems, however, these edge states can also exist for topologically trivial bands, a phenomenon known as anomalous Floquet topological insulators. While the identification of such phases usually requires the measurement of the edge states, we find that the dynamics of initially localized wave packets during the driving period also identifies the phase by tracing out a finite area. This constitutes a feasible proxy for anomalous topology that will help in studying these phases.

The preprint is available at Asteria et al.