Group Seminar via Zoom: Feshbach resonances in a hybrid atom-ion system

February 02, 2021

Pascal Weckesser, University of Freiburg
Group meeting via video conference (Zoom)
Tuesday, February 2nd, 09:00 (MEZ)

Dealing with the unique situation of partial lock downs worldwide and home office solutions at our Institute due to the current spreading of the Covid 19 virus, we are now holding our group seminars and journal clubs via video conference.
This procedure enables us to continue our research, enhance discussions and exchange important information.


The fields of ultracold atoms and trapped ions are important pillars of experimental quantum optics. Recently the expertise of both fields has been combined in hybrid trapping setups [1] with the aim to prepare atom-ion mixtures at low temperatures close to the few-partial wave regime. There, new quantum phenomena such as atom-ion Feshbach resonances [2] and the formation of mesoscopic, weakly bound molecules [3] have been predicted. However, reaching the ultracold regime in hybrid setups is a challenging task, as intrinsic micromotion heating effects of conventional radio- frequency (rf) traps [4] limit most experiments. In our experiments in Freiburg, we follow two pathways to overcome these heating effects allowing us to enter the few-partial wave regime. On the one hand, we choose an atom-ion mixture with high
mass imbalance – 6Li atoms and 138Ba+ ions – as comparably heavy ions are subject to less heating [4,5] . On the other hand, we have developed optical dipole traps for ions [6] allowing us to probe atom-ion interactions in complete absence of rf fields [7].
In this talk, I present our latest advancements in optical ion trapping [8] and demonstrate the first observation of Feshbach resonances between Ba+ ions and Li atoms. The presence of a Feshbach resonance gives rise to enhanced inelastic processes, with three-body recombination being the predominant ion loss channel. In the future, we want to apply these resonances to further control the ion’s sympathetic cooling rate, leading to colder temperatures down to the s-wave regime.

[1] A. Haerter et al., Contemporary Physics, volume 55, issue 1, pages 33-45 (2014).
[2] M. Tomza et al. Reviews of Modern Physics 91.3 (2019): 035001.
[3] R. Cote et al.Physical review letters 89.9 (2002): 093001.
[4] M.Cetina et al., Physical review letters 109,253201 (2012)
[5] T. Feldker et al. Nature Physics (2020): 1-4.
[6] A. Lambrecht et al., Nature Photonics 11.11 (2017): 704.
[7] J. Schmidt et al.  Physical Review Letters 124.5 (2020): 053402.
[8] P. Weckesser et al. Physical Review A 103,013112(2021)

If you would like to join our group seminars via Zoom, please contact us for more information.

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