Quantum optical phenomena in two-dimensional materials (Keynote Presentation)

Atomically thin materials offer a robust platform for nanoscale light manipulation, featuring a diversity of polaritonic behavior in the form of plasmons in metals, excitons in transition metal dichalcogenides, and phonons in ionic insulators. In this context, we will present recent advances in ultrathin crystalline noble-metal films as promising plasmonic platforms for active nanophotonics. We discuss their optical response characteristics using models ranging from simple phenomenological approaches to a full quantum-mechanical treatment. In addition, we discuss the in/out coupling problem between external light and strongly confined polaritons, which remains a major challenge, and for which we propose innovative solutions based on critical coupling between dipolar scatterers and planar interfaces. We further discuss a disruptive approach to the design of polaritonic materials relying on quantum phase effects, as well as a new mechanism of electron-positron pair production based on the scattering between gamma-rays and surface polaritons.