SPICE Workshop on Spin textures: Magnetism meets Plasmonics, July 23rd - 25th 2024
Tim Davis
Surface plasmon polaritons (SPPs) are surface charge waves excited on metal surfaces by light. The electric fields arising from these charges rotate, creating a spin transverse to the direction of propagation. The interference of many of these waves can give rise to distributions of spin vectors that exhibit the three dimensional topology of a skyrmion or a meron, as one finds in thin magnetic films. However, the similarity of these topologies with magnetic fields is only local and measures of the topology, such as the Chern number, usually fail when applied globally. Despite the spin fields having only local topologies akin to magnetic systems, the in-plane spin vectors of SPPs are constrained by a global topology as expressed in the Poincaré-Hopf theorem. In this talk I will briefly introduce the physics of surface plasmons, present some of the local topologies created by the spin vectors of SPPs excited from circular and spiral boundaries and discuss the arguments used to characterise their topology and how the Poincaré-Hopf theorem leads to a kind of conservation law for the in-plane components of the spin.