Cooperative emission by two different atoms into surface plasmons

Abstract

The interaction between surface plasmons and two atoms with different electronic transition frequencies near a metal or doped semiconductor surface is considered. The atom-atom and atom-surface separations are assumed to be smaller than the corresponding mean resonance wavelength. The time evolution of the emission rate of such an atomic pair into surface plasmon modes is calculated in a fully quantum-mechanical manner. Explicit results are given for various initial states of the diatomic system. As the frequency difference Δ ⩽ γ, where γ is the mean half-width of the atomic resonance lines, the emission behaves as if there are two identical atoms. On the other hand, when Δ > γ, oscillations are found in the emission rate as a function of time in all casese as a manifestation of beating. The oscillations are especially pronounced when the diatomic system is initially in a coherent state. For the form of the particular state corresponding to complete photon trapping in the case of two identical atoms, a pair of two different atoms exhibits oscillating emission into the superradiant region before eventual decay to zero.