University of Freiburg
Institute of Physics
Experimental Atomic, Molecular, and Optical Physics
alexander.doering(at)physik.uni-freiburg.de
Exploration of long-range interactions and quantum simulation using hybrid atom-ion systems
A central objective is the investigation of the collisional dynamics between a single, trapped 138Ba+ ion and an ultracold gas of 6Li atoms. This specific mixture is highly advantageous due to the large mass imbalance which helps to suppress the heating effects typically associated with radio-frequency Paul traps. This allows reaching the s-wave regime where scattering is described by the lowest partial waves.
The primary experimental tool for controlling these interactions is the use of magnetically tunable Feshbach resonances. These resonances occur when the energy of an open scattering channel matches the energy of a closed-channel molecular bound state, allowing for the precise manipulation of the atom-ion interaction strength.
The detection of these resonances is performed through ion-loss spectroscopy. By scanning the external magnetic field and monitoring the survival probability of the ion, one can identify resonant features where the ion loss rate increases significantly. This loss is primarily driven by three-body recombination, a process in which the ion and two atoms collide to form a molecular ion, releasing sufficient kinetic energy for the ion to escape the trap. Studying these collisional complexes provides fundamental insights into cold chemistry and paves the way for the simulation of many-body physics, such as the formation of ionic polarons in a degenerate Fermi gas.
References
1. Thielemann, F. et al. Exploring Atom-Ion Feshbach Resonances below the s -Wave Limit. Phys. Rev. X15, 011051 (2025).
2. Weckesser, P. et al. Observation of Feshbach resonances between a single ion and ultracold atoms. Nature600, 429–433 (2021).
3. Weckesser, P. et al. Trapping, shaping, and isolating of an ion Coulomb crystal via state-selective optical potentials. Phys. Rev. A103, 013112 (2021).
4. Giannakeas, P., Khaykovich, L., Rost, J.-M. & Greene, C. H. Nonadiabatic Molecular Association in Thermal Gases Driven by Radio-Frequency Pulses. Phys. Rev. Lett.123, 043204 (2019).
Supervisor: Tobias Schätz
