Atoms near magnetodielectric bodies: van-der-Waals energy and Casimir-Polder force

Based on macroscopic QED in linear, causal media, we present a consistent theory for the Casimir-Polder force acting on an atom positioned near dispersing and absorbing magnetodielectric bodies. The perturbative result for the van-der-Waals energy is shown to exhibit interesting new features in the presence of magnetodielectric bodies. To go beyond perturbation theory, we start with the center-of-mass equation of motion and derive a dynamical expression for the Casimir-Polder force acting on an atom prepared in an arbitrary electronic state. For a non-driven atom in the weak coupling regime, the force as a function of time is shown to be a superposition of force components that are related to the electronic density matrix elements at chosen time. These force components depend on the position-dependent polarizability of the atom that correctly accounts for the body-induced level shifts and broadenings.