Superradiant properties of a suspension of composite nanoparticles

The characteristics of gold nanoparticles coated with silicon dioxide containing embedded dye molecules are experimentally investigated at room and liquid-nitrogen temperatures. The origin of the observed narrowing of the luminescence line upon cooling is discussed. Model analysis of the nanosystem under study indicates that the observed behavior cannot be related to the temperature dependence of individual parameters of the components of the medium. The effect is explained by the occurrence of nonlinear feedback that leads to the enhancement of phase synchronization between the polarizations of the active transitions in the dye molecules and plasmons. This effect is an analog of plasmon polariton superradiance.