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