Observation of Floquet solitons in a topological bandgap

• DOI: 10.1126/science.aba8725
• Publication Date: 2020-05-21T23:02:25Z
• Authors: Sebabrata Mukherjee; Mikael C. Rechtsman
• Keywords: Floquet theory; Topological insulator; Lattice (music)

Topological materials exhibit properties dictated by quantised invariants that make them robust against perturbations. This topological protection is a universal wave phenomenon applies not only in the context of electrons solid-state but also to photonic systems, ultracold atoms, mechanical circuits, exciton-polaritons and beyond. However, vast majority research these systems has focused on linear domain, i.e., where inter-particle interactions do play role. Here, we experimentally observe solitons -- waves propagate without changing shape as result nonlinearity bulk Floquet insulator. These fundamentally different behaviour than ordinary band gaps they execute cyclotron-like orbits are associated with topology lattice. Specifically, employ laser-written waveguide array periodic variations along axis give rise non-zero winding number, arises from optical Kerr effect ambient glass. The described here applicable range bosonic due its description focusing nonlinear Schr\"odinger equation, Gross-Pitaevskii equation attractive interactions.