Retardation effects on the Efimov states

The retardation effect causes a small but finite change in the two-body potential, which in turn results in a large reduction in the scattering length A when the strength is near its critical value for forming a zero-energy bound state. This coupling to the vacuum fluctuation field thus affects the two-body dynamics such that the Efimov phenomenon is destroyed. Enhanced response of the scattering length ΔA for a small change in the two-body potential may be employed to gain efficiency and accuracy in experiments; for example, in testing body bound states in a cold atomic gas. The retardation effect can remove several Efimov bound states, depending on how large the change in scattering length is. Manipulation of the two-body potential by external fields is suggested to modify or eliminate some Efimov states. The optimal choice suggested from this analysis is to manipulate A such that A/ΔA≪1. Also included is a discussion on the additivity correction to the two-body polarization potential due to the Casimir effect.