We report a transient plasmonic spin skyrmion topological quasiparticle within surface plasmon polariton vortices, which is described by analytical modeling and imaging of its formation by ultrafast interferometric time-resolved photoemission electron microscopy. Our model finds a twisted skyrmion spin texture on the vacuum side of a metal/vacuum interface and its integral opposite counterpart in the metal side. The skyrmion pair forming a hedgehog texture is associated with co-gyrating anti-parallel electric and magnetic fields, which form intense pseudoscalar E·B focus that breaks the local time-reversal symmetry and can drive magnetoelectric responses of interest to the axion physics. Through nonlinear two-photon photoemission, we record attosecond precision images of the plasmonic vectorial vortex field evolution with nanometer spatial and femtosecond temporal (nanofemto) resolution, from which we derive the twisted plasmonic spin skyrmion topological textures, their boundary, and topological charges; the modeling and experimental measurements establish a quantized integer photonic topological charge that is stable over the optical generation pulse envelope.
Topology is an intrinsic property of the orbital symmetry and elemental spin–orbit interaction, but also, intriguingly, designed vectorial optical fields can break existing symmetries, to impose (dress) topology through coherent interactions with trivial materials. Through photonic spin–orbit interaction, light can transiently turn on topological interactions, such as chiral chemistry, or induce non-Abelian physics in matter. Employing electromagnetic simulations and ultrafast, time-resolved photoemission electron microscopy, we describe the geometric transformation of a normally incident plane wave circularly polarized light carrying a defined spin into surface plasmon polariton field carrying orbital angular momentum which converges into an array of plasmonic vortices with defined spin textures. Numerical simulations show how within each vortex domain, the photonic spin–orbit interaction molds the plasmonic orbital angular momentum into quantum chiral spin angular momentum textures resembling those of a magnetic meron quasiparticles. We experimentally examine the dynamics of such meron plasmonic spin texture lattice by recording the ultrafast nanofemto plasmonic field evolution with deep subwavelength resolution and sub-optical cycle time accuracy from which we extract the linear polarization, L-line singularity distribution, that defines the periodic lattice boundaries. Our results reveal how vectorial optical fields can impress their topologically nontrivial spin textures by coherent dressing or chiral excitations of matter.
Spin and field textures define the
topology of the electric
and
magnetic fields in vacuum. These textures can be imposed on matter
by light–matter interactions on the nanometer spatial and DC
to femtosecond time scales to define the spatial and temporal symmetries
of quasiparticle interactions. How to define the topology of thermodynamically
evolving or dynamically imposed polaritonic textures is still an open
question in applying control parameters such as temperature or phase
of structured light. In this Perspective, we specifically consider
the spin topology of geometrical plasmonic lattices formed by surface
plasmon polariton fields spanning the full range of polygonal symmetries,
ranging from the triangular to the circular including the intermediate
aperiodic quasicrystalline tilings. Our premise is that the distortion
of a triangular or a square lattice into a circular one, without introducing
discontinuous geometric change, as by cutting, must preserve the polariton
topology. From this perspective, we review the recent studies of stable
optical field-induced dynamic quasiparticles with topological spin
textures on the nanoscale. Specifically, we draw attention to how
the topological spin textures evolve through the continuous deformation
of the surface plasmon generating polygon geometries from triangular
to circular. The goal of this Perspective is to introduce the topological
properties of plasmonic vortices and to expand the discussion and
understanding of how their topological spin and field textures dress
material properties for exploration of fundamental physics and applications
in photonics and spintronics.
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