Pseudo-spin internal structure for plasmons and anomalous geometric phase

The collective plasmonic modes of two-dimensional metals comprise a simple pattern of oscillating charge density that yields enhanced light-matter interaction. Here we unveil that beneath this familiar facade, plasmons possess a hidden geometrical internal structure that fundamentally alters its dynamics. This structure comprises the local current density configuration of the electrons that form the plasmon and can take on an intricate pattern when a magnetic field is applied, exhibiting a non-trivial texture. When these plasmons scatter, their non-trivial internal structure allows them to pick up non-trivial geometric phases (tunable by hall conductivity) and can even translate its trajectory by multiple plasmon wavelengths when it is reflected off a boundary. The internal “spinor”-type structure of plasmons reveals uncharted territory for plasmonics with new ways to manipulate their trajectories, and a new playground to explore the geometry of quasiparticles.