Improving Efficiency of Sympathetic Cooling in Atom-Ion and Atom-Atom Confined Collisions

Abstract

We propose a new way for sympathetic cooling of ions in an electromagnetic Paul trap: it implies the use for this purpose of cold buffer atoms in the region of atom-ion confinement-induced resonance (CIR). The problem is that the unavoidable micromotion of the ion and the long-range nature of its interaction with the environment of colder atoms in a hybrid atomic-ion trap prevent its sympathetic cooling. We show that the destructive effect of ion micromotion on its sympathetic cooling can however be suppressed in the vicinity of the atom-ion CIR. The origin of this is the "fermionization" of the atom-ion wave function near CIR, where the atom-ion pair behaves as a pair of noninteracting identical fermions. This prevents the complete approach of the atom with the ion near resonance and does not enhance the ion micromotion, which interferes with its sympathetic cooling. We investigate the effect of sympathetic cooling around CIRs in atom-ion and atom-atom confined collisions within the qusiclassical-quantum approach using the Li-Yb$^+$ and Li-Yb confined systems as an example. In this approach, the Schr\"odinger equation for a cold light atom is integrated simultaneously with the classical Hamilton equations for a hotter heavy ion or atom during collision. We have found the region near the atom-ion CIR where the sympathetic cooling of the ion by cold atoms is possible in a hybrid atom-ion trap. We also show that it is possible to improve the efficiency of sympathetic cooling in atomic traps by using atomic CIRs.