Plasmonic twistronics: skyrmion bags in two- and three layer structures

Twistronics has revolutionized solid state physics in the last few years. The discovery of twisted bilayer graphene enabled switchable superconductivity and switchable Mott-insulator transitions. Similarly, surface plasmon polaritons can exhibit topological structures, such as plasmonic skyrmions. Using vector-resolved PEEM with a sub-10 nm spatial and sub-fs temporal resolution, it is possible to generate entire movies of the vector fields of surface plasmon polaritons and analyze their topological structures. Besides Neel skyrmions, it is also possible to create merons, meron pairs, as well as complex higher dimensional topologies when using quasicrystals. Furthermore, the investigation of fractional orbital angular momentum is also possible. Specifically, we demonstrate the existence of plasmonic skyrmion bags in two-layer twisted structures for magic twist angles. Depending on the exact symmetry point, it is possible to generate skyrmion bags with two, three, four, and more than 10 skyrmions inside, characterized by a total skyrmion number of N-1 (as the bag itself has a skyrmion number of -1). Three-layer twisted structures reveal complex skyrmion bag superlattices.