Joachim Siemund (f. Welz)

Feshbach Resonances in a hybrid Atom-Ion System

We (the group of Prof. Tobias Schätz) recently presented the first observation of Feshbach resonances between neutral atoms and ions. These resonances – a quantum phenomenon only observable at ultracold temperatures – allow the interaction rate between particles to be tuned with the perspective to even switch them off. While Feshbach resonances are commonly utilized in neutral atom experiments, reaching the ultracold regime in hybrid rf-optical traps is challenging, as the driven motion of the ion by the rf trap limits the achievable collision energy. By immersing a single Ba ion in an ultracold cloud of Li, we measured the enhancement of both two-body and three-body interactions through changes in the ion’s internal and motional energy. This paves the way for all-optical trapping of both species, circumventing the fundamental rf-heating, and for new applications, such as the coherent formation of molecular ions and simulations of quantum chemistry.

Supervisor: Tobias Schätz