Observation of a Strong Atom-Dimer Attraction in a Mass-Imbalanced Fermi-Fermi Mixture

Michael Jag ^{1, 2} Matteo Zaccanti ^{1, 3} Marko Cetina ¹ Rianne S. Lous ^{1, 4} Florian Schreck ¹ Rudolf Grimm ^{1, 4} Dmitry S. Petrov ⁵ Jesper Levinsen ^{6, 7}

Physical Review Letters, American Physical Society, 2014, 112, pp.075302

We investigate a mixture of ultracold fermionic $^{40}$K atoms and weakly bound $^{6}$Li$^{40}$K dimers on the repulsive side of a heteronuclear atomic Feshbach resonance. By radio-frequency spectroscopy we demonstrate that the normally repulsive atom-dimer interaction is turned into a strong attraction. The phenomenon can be understood as a three-body effect in which two heavy $^{40}$K fermions exchange the light $^{6}$Li atom, leading to attraction in odd partial-wave channels (mainly p-wave). Our observations show that mass imbalance in a fermionic system can profoundly change the character of interactions as compared to the well-established mass-balanced case.

• 1. Institut für Quantenoptik und Quanteninformation
• 2. Institut fur Experimentalphysik
• 3. CNR – Istituto Nazionale Ottica
• 4. Institut fur Experimentalphysik
• 5. LPTMS – Laboratoire de Physique Théorique et Modèles Statistiques
• 6. TCM Group, Cavendish Laboratory
• 7. Aarhus Institute of Advanced Studies