Periodic Reporting for period 1 - Pint (Probing interactions between a charged impurity and a cold atomic bath in the quantum regime)
Berichtszeitraum: 2020-06-01 bis 2022-05-31
Hybrid ion-atom systems combine the well-controllable platforms of trapped ions and ultracold quantum gases and link them together by the intermediate-range ion-atom interaction. These new quantum systems offer intriguing prospects for buffer gas cooling, quantum simulation of condensed matter/many-body systems as well as for state-to-state quantum chemistry. Although ultracold atoms and ions have each been routinely studied in the quantum regime, experiments with ion-atom mixtures remained firmly confined to the classical collision regime until very recently. As a first, the Yb+ - Li mixture has been cooled to the regime where quantum effects dominate the ion-atom interactions. With this unique system, the MSCA IF Fellowship's aim was to understand, characterize, and control the ion-atom interaction in the quantum regime trough new experiments.
The investigations focused on the experimental characterization, buffer gas cooling and quantum chemistry. We could numerically show that the system could become twice as cold by careful optimization of the ion trap parameters and thus probe deeper into the quantum regime. Furthermore, we created a bath of Feshbach dimers and measured the molecular ion formation that followed when combing the bath with the ion. This demonstrated the sensing capabilities of a trapped ion in probing as little as 50 dimers in a bath of 20 000 atoms. These results were published in four peer-reviewed publications: Hirzler et al., Phys. Rev. A 102, 033109 (2020), Hirzler et al., Phys. Rev. Res. 2, 033232 (2020), Trimby et al., New J. Phys. 24, 035004 (2022) and Hirzler et al., Phys. Rev. Lett. 128, 103401 (2022). Furthermore, the knowledge obtained on ultracold ion-atom systems was reviewed and summarized as a chapter in Advances In Atomic, Molecular, and Optical Physics (Lous and Gerritsma, AAMOP 71, 65-133 (2022)).
The Marie Curie action offered a great possibility to combine the applicant’s expertise on ultracold atoms together with the expertise of the host group in ion-atom systems. Our numerical study showed a route towards reaching deeper into the quantum regime with time-dependent traps and presents buffer gas cooling as a feasible alternative to laser cooling techniques. These insights and available simulations are useful when designing new ion-atom experiments. The molecular ion measurements present a novel approach towards the creation of cold molecular ions and point to the exploration of ultracold chemistry in ion molecule collisions. It also provides a new method to detect low-density molecular gases with a high sensitivity.