SAMOP 2021 – scientific programme

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MO: Fachverband Molekülphysik

MO 8: Cold Molecules

MO 8.7: Talk

Friday, September 24, 2021, 12:15–12:30, H1

Generating degenerate ²³Na⁴⁰K molecules through a quantum phase transition — •Marcel Duda, Xing-Yan Chen, Andreas Schindewolf, Roman Bause, Richard Schmidt, Jonas von Milczewski, Immanuel Bloch, and Xin-Yu Luo — Max-Planck-Institut für Quantenoptik, Garching, Germany

A decade after the first creation of bi-alkali polar molecules, reaching quantum degeneracy remains a challenge even when associating a degenerate mixture of atoms. Starting from a mixture of bosonic and fermionic atoms, the bottleneck lies in the efficient association of weakly-bound Feshbach molecules. The density mismatch, severe loss, and consequent heating prevent the exploration of the Bose-Fermi mixture in the strongly interacting regime and, thus, the Feshbach association. We eliminate the detrimental loss by decompressing a Bose-Einstein condensate (BEC) of sodium to density-match it with a degenerate Fermi gas of potassium. By doing so, we can associate 50000 long-lived ²³Na⁴⁰K Feshbach molecules below 0.3 of the Fermi temperature. We characterize the association through the depletion of the condensate fraction and observe a good agreement with theoretical predictions of a phase transition from polarons to molecules. The degeneracy is underlined by partially restoring a BEC when reversing the association ramp. In the last step, we produce 30000 ²³Na⁴⁰K polar molecules at an effective temperature of half the Fermi temperature.