Synthetic Spatiotemporal Plasmonic Vortices on Chip

Spatiotemporal vortices are polychromatic modes that intertwine orbital angular momentum in space and time. Here, we introduce a new class of such vortices, "spatiotemporal plasmonic vortices," carrying nontrivial topological spin textures. They are generated by chronotopic interference of temporally delayed plasmonic eigenvortices, where a π-phase dislocation in the space-frequency domain maps into a 2π spiraling phase in space-time, with the resulting focus-defocus dynamics emulating U(1) gauge transitions. Using interferometric time-resolved photoemission electron microscopy, we directly image their nanometer-attosecond evolution and control vortex number and position. Quantum-path analysis of coherent two-photon photoemission processes reveals the nonlinear plasmonic polarization fields and angular-momentum conservation, establishing spatiotemporal plasmonic vortices as a platform for probing spatiotemporally structured quantum matter.