Radiative spontaneous decay enhancement near an ultrathin plasmonic film

We develop a quantum electrodynamics theory for the spontaneous decay process of a point dipole emitter near a thin metallic film. It was previously shown that the strong vertical electron confinement causes the film plasma frequency to become spatially dispersive[1], resulting in a (confinement induced) nonlocal dielectric response of the film[2]. Using this fact we calculate the electromagnetic Green's function and the emitter-to-surface distance dependence for the dipole spontaneous decay rate near the metallic film of finite thickness. We show that the confinement induced dielectric response nonlocality of the ultrathin films can result in a two-order-of-magnitude radiative decay rate enhancement relative to vacuum. The effect can be qualitatively understood in terms of the interacting image dipoles and can be controlled by varying the material composition, the thickness and the surroundings of the film. The inelastic electron scattering diminishes the effect. These are the universal peculiarities of the light-matter interactions in close proximity to ultrathin plasmonic nanostructures. -- [1] I.V.Bondarev & V.M.Shalaev, Opt. Mater. Expr. 7, 3731 (2017); [2] I.V.Bondarev, H.Mousavi, & V.M.Shalaev, MRS Commun. 8, 1092 (2018).