The Birth of a Plasmonic Topological Quasiparticle on the Nanofemto Scale

Abstract: At interface of the classical and quantum physics Maxwell and Schr\"odinger equations describe how optical fields drive and control electronic phenomena at THz or PHz frequencies and on ultra-small scales to enable lightwave electronics. Light striking a metal surface triggers electric field-electron particle/wave interactions to coherently imprint and transfer its attributes on the attosecond time scale. Here we create and image by ultrafast photoemission electron microscopy a new quasiparticle of optical field-collective electron interaction where the design of geometrical phase creates a plasmonic topological spin angular momentum texture. The spin texture resembles that of magnetic meron quasiparticle, is localized within 1/2 wavelength of light, and exists on ~20 fs (2^10-14 s) time scale of the plasmonic field. The quasiparticle is created in a nanostructured silver film, which converts coherent linearly polarized light pulse into an evanescent surface plasmon polariton light-electron wave with a tailored geometric phase to form a plasmonic vortex. Ultrafast coherent microscopy imaging of electromagnetic waves propagating at the local speed of light of 255 nm/fs, electromagnetic simulations, and analytic theory find a new quasiparticle within the vortex core, with topological spin properties of a meron that are defined by the optical field and sample geometry. The new quasiparticle is an ultrafast topological defect whose chiral field breaks the time-inversion symmetry on the nanoscale; its creation, symmetry breaking topology, and dynamics pertain to contexts ranging from the cosmological structure creation to topological phase transitions in quantum liquids and gases, and may act as a transducer for quantum information on the nanofemto scale.