Ion solvation in atomic baths: From snowballs to polarons

Solvation, the result of the complicated interplay between solvent–solute and solvent–internal interactions, is one of the most important chemical processes. Consequently, a complete theoretical understanding of solvation seems like a heroic task. However, it is possible to elucidate fundamental solvation mechanisms by looking into simpler systems, such as ion solvation in atomic baths. In this work, we study ion solvation by calculating the ground state properties of a single ion in a neutral bath from the high-density to the low-density regimes, finding common ground for these two, in principle, disparate regimes. Our results indicate that a single ¹⁷⁴Yb⁺ ion in a bath of ⁷Li atoms forms a coordination complex at high densities with a coordination number of 8, with strong electrostriction characteristic of the snowball effect. On the contrary, treating the atomic bath as a dilute quantum gas at low densities, we find that the ion-atom interaction's short-range plays a significant role in the physics of many-body-bound states and polarons. Furthermore, in this regime, we explore the role of an ion trap necessary to experimentally realize this system, which drastically affects the binding mechanism of the ion and atoms from a quantum gas. Therefore, our results give a novel insight into the universality of ion-neutral systems in the ultracold regime and the possibilities of observing exotic many-body effects. Keypoints: A global study of ion solvation in atomic baths from the high- to the low-density regimes. The ion–atom short-range interaction is critical to understanding the presence of many-body-bound states and polarons. The ion-trapping potential drastically impacts many-body-bound states and polaron formation.