Exchange effects on cooperative radiation interaction in a two-atom model.

Abstract

We study cooperative effects on the radiation interaction of a pair of two-level atoms with a spatial separation r\ensuremath{\ll}${\ensuremath{\lambda}}_{0}$ much closer than the optical wavelength of the dipole transition. In this regime we allow for charge exchange between the atoms (hybridization), which leads to qualitatively different behavior in contrast to an isolated pair of atoms because of the presence of the monopole Coulomb interaction. The interaction of the atoms with the radiation field and an external classical driving field is treated within a master equation approach. The numerical as well as the analytical results indicate the existence of quantum beats in the radiative decay of the system. In the case of an external driving field the system shows a dark resonance for a fixed detuning independent of the strength of the external field.