CMT Seminar: Justin Song

National Research Foundation Fellow, and Nanyang Assistant Professor of Physics
Song Research Group, Nanyang Technological University

Plasmon geometric phase

Plasmons are essential in squeezing and enhancing light-matter interaction on the nanoscale, such as in bioimaging, on-chip communication, and photodetection. While manipulating, exploiting, and probing plasmons in quantum materials and heterostructures continues to be a field of intense (and recent) research interest, on a fundamental physics level, plasmons in simple metals are typically regarded as fairly structureless collective charge density oscillations with a vanilla behavior described entirely by its dispersion and lifetime.

I will discuss how this perspective is far from complete. Conventionally, deep subwavelength plasmons can be described by their charge density and its electric fields alone. I will unveil how plasmons in simple 2D metals can possess an additional hidden internal structure that can dramatically alter its dynamics and evolution. 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.