Topological pumping in a Floquet-Bloch band

TL;DR

This paper demonstrates topological pumping in a simple sinusoidal lattice using two-tone Floquet driving, enabling the engineering of topological matter without complex lattice structures or strong magnetic fields.

Contribution

It provides the first experimental implementation of topological pumping in a Floquet-Bloch band with simple lattice potentials and two-tone driving, simplifying topological material engineering.

Findings

Successful adiabatic preparation of Floquet bands avoiding gap closings

Induction of topological pumping through cyclic modulation of drive parameters

System well described by an effective Shockley model

Abstract

Constructing new topological materials is of vital interest for the development of robust quantum applications. However, engineering such materials often causes technological overhead, such as large magnetic fields, specific lattice geometries, strong spin-orbit coupling, synthetic dimensions, or dynamical superlattice potentials. Simplifying the experimental requirements has been addressed on a conceptual level - by proposing to combine simple lattice structures with Floquet engineering - but there has been no experimental implementation. Here, we demonstrate topological pumping in a Floquet-Bloch band using a plain sinusoidal lattice potential and two-tone driving with frequencies $\omega$ and $2\omega$. We adiabatically prepare a near-insulating Floquet band of ultracold fermions via a frequency chirp, which avoids gap closings en route from trivial to topological bands. Subsequently, we induce topological pumping by slowly cycling the amplitude and the phase of the $2 \omega$ drive. Our system is well described by an effective Shockley model, establishing a novel paradigm to engineer topological matter from simple underlying lattice geometries. This approach could enable the application of quantised pumping in metrology, following recent experimental advances on two-frequency driving in real materials.