Quantum plasmonics: longitudinal quantum plasmons in copper, gold, and silver

The propagation of plasmonic waves in various metallic quantum nanostructures has received considerable attention for its applications in technology. The quantum plasmonic properties of metallic nanostructures in the quantum size regime have been difficult to describe using an appropriate model. Here nonlocal quantum plasmons are investigated in the most important metals of copper, gold, and silver. The dispersion properties of these metals and the propagation of longitudinal quantum plasmons in the high photon energy regime are studied using a new model of nonlocal quantum dielectric permittivity. The epsilon-near-zero properties are investigated and the spectrum and the damping rate of the longitudinal quantum plasmons are obtained in these metals. The quantum plasmons' wave function is shown for both the classical and quantum limits. It is shown that silver is the most appropriate for quantum metallic structures in the development of next-generation quantum optical and sensing technologies, due to its low intrinsic loss.