# Mainz 2017 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 46: Quantum Gases: Fermions I

### Q 46.6: Vortrag

### Donnerstag, 9. März 2017, 12:30–12:45, P 204

**Phase Separation in a Bose-Fermi Mixture of **^{41}**K and **^{6}**Li** — •Rianne S. Lous^{1,2}, Bo Huang^{1}, Isabella Fritsche^{1,2}, Fabian Lehmann^{1,2}, Michael Jag^{1,2}, Emil Kirilov^{1,2}, and Rudolf Grimm^{1,2} — ^{1}IQOQI, Austrian Academy of Sciences, Innsbruck, Austria — ^{2}Institute for Experimental Physics, University of Innsbruck, Innsbruck, Austria

We report on the observation of phase separation between a ^{41}K Bose-Einstein condensate (BEC) and a ^{6}Li Fermi sea with strong repulsive interspecies interactions. After evaporation in an optical dipole trap, we obtain 10^{4} ^{41}K atoms with a 55 % BEC fraction and a Fermi sea of 10^{5} ^{6}Li atoms with a *T*/*T*_{F} < 0.07. We explore this double-degenerate mixture by tuning the heternonuclear interaction with the use of a Feshbach resonance at 335.8 G. We observe the phase separation by measuring the breathing-mode frequency of the bosons and their lifetimes for varying interaction strength. We see an increase in frequency when interactions become strongly repulsive and a decrease in loss rate.
To understand our loss rate results, we calculate the spatial overlap between the two components with a mean-field model beyond local density approximation (LDA) and attribute the losses to the three-body recombination.
We also calculate the breathing-mode frequency on a LDA level. Both theoretical models fit nicely to our experimental results. This work is supported by the Austrian Science Fund FWF within SFB FoQuS.