Floquet Engineering Topological Dirac Bands
We experimentally realized a time-periodically modulated 1D lattice for ultracold atoms featuring a pair of linear bands, each with a Floquet winding number. These bands are spin-momentum locked and almost perfectly linear everywhere in the Brillouin zone: a near-ideal realization of the 1D Dirac Hamiltonian. We characterized the Floquet winding number using a form of quantum state tomography, covering the Brillouin zone and following the micromotion through one Floquet period. Last, we altered the modulation timing to lift the topological protection, opening a gap at the Dirac point that grew in proportion to the deviation from the topological configuration.
Floquet Engineering Topological Dirac Bands; M. Lu, G. H. Reid, A. R. Fritsch, A. M. Piñeiro, and I. B. Spielman; Phys. Rev. Lett. 129 040402 (2022). doi:10.1103/PhysRevLett.129.040402