Spatiotemporal Optical Vortex Polariton

We confirm the existence of a new bulk medium quasiparticle with transverse orbital angular momentum (tOAM) and elucidate its physical origin. The tOAM structure is driven by torques induced by the ponderomotive force of the light in the medium, originating from the magnetic Lorentz force, even for weak light fields. There are two contributions to the material tOAM: One part depends on the pulse spatial shape change as it passes through an interface and the other part depends on medium dispersion. The results, from first principles particle-in-cell simulations of a simple plasma, are in excellent agreement with our theory for general dielectric media [S. W. Hancock et al., Phys. Rev. Lett. 127, 193901 (2021)]. For plasma, there is agreement up to near-critical densities and near-relativistic field strengths.