We describe a stable topological configuration of optical spin angular momentum (SAM) at the core of a plasmonic vortex that has a Néel type magnetic Skyrmion texture, and experimentally demonstrate its existence by interferometric time-resolved photoemission electron microscopy (ITR-PEEM). Skyrmions are stable quasiparticles in magnetic materials with distinct topological spin textures, which occur in systems that lack of time-reversal symmetry. Our proposed optical spin Skyrmion is generated at the core of a surface plasmon polaritons (SPPs) vortex, which is launched by linearly polarized femtosecond laser pulses at an Archimedean plasmonic coupling structure. The time-reversal symmetry of the system is broken due to the magnetic field generated by the orbiting charge density waves. Such optical spin configuration is established as the formation of the SPPs vortex, and has the lifetime of the duration of the excitation pulse. Using ultrafast ITR-PEEM, we experimentally resolve the plasmonic vortex formation and evolution by imaging its in-plane field components, with ~10 nm and ~100 as spatial-temporal scan resolution. Finally, the optical flow of the experimental plasmonic vortex overlaps with the numerically calculated optical L-line singularity of the vortex fields and the Skyrmion density distribution, which we use as a defining locator of the optical spin Skyrmion. The study of optical spin Skyrmions on femtosecond time scale can model cosmological structure formation, symmetry breaking phase transitions in quantum liquids, and provide novel quasiparticles for quantum information processing.

Revealing an optical spin skyrmion at the core of a plasmonic vortex

2019 Fall National Meeting

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