SPICE Workshop on Spin textures: Magnetism meets Plasmonics, July 23rd - 25th 2024
Pascal Dreher
The strong interaction of light with fundamental dipolar excitations of matter can result in the formation of hybrid light-matter quasiparticles, so-called polaritons. On solid-state surfaces, such polaritons can constitute a dominant part of the optical response and can be thought of as bound evanescent electromagnetic waves with dispersion relations depending on the details of the involved dipolar excitations. Surface plasmon polaritons (SPPs) are a prominent example of such waves, where an electron density wave at a metal surface, i.e., a surface plasmon, hybridizes with light. Their technological relevancy ranges from medieval stained-glass windows over PCR tests and bio-sensing applications to light-harvesting and photochemistry applications.
From the fundamental perspective of this workshop, SPPs are interesting because they can exhibit spatio-temporally dependent vectorial spin and orbital angular momentum with great analogy to the spin textures found in magnetism. Being vector fields themselves, SPPs and the derived angular momenta can be topologically non-trivial and need to obey similar topological laws as for magnetic spin textures. Great control over the topological vectorial textures of SPPs can be exerted by appropriate nanostructuring of surfaces, which enables mimicking of many topological excitations found in magnetism.
In this tutorial, I will review the theoretical and experimental fundamentals of SPPs. I will discuss their physical properties, how they are excited and how their vectorial field properties can be measured. To conclude this introduction, I will give a brief overview over the application of topology to the field of surface plasmon polaritons.