title: Observation of a strong atom-dimer attraction in a mass-imbalanced Fermi-Fermi mixture.
abstract: We investigate a mixture of ultracold fermionic K40 atoms and weakly bound Li6K40 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 K40 fermions exchange the light Li6 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.
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Jag
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and CNR Istituto Nazionale Ottica, 50019 Sesto Fiorentino, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Zaccanti
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.
authors.forename: Marko
authors.initials: M
authors.lastname: Cetina
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Rianne S
authors.initials: RS
authors.lastname: Lous
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.
authors.forename: Florian
authors.initials: F
authors.lastname: Schreck
authors.affiliation: Institut für Quantenoptik und Quanteninformation (IQOQI), Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Grimm
authors.affiliation: Université Paris-Sud, CNRS, LPTMS, UMR8626, Orsay F-91405, France.
authors.forename: Dmitry S
authors.initials: DS
authors.lastname: Petrov
authors.affiliation: TCM group, Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom and Aarhus Institute of Advanced Studies, Aarhus University, DK-8000 Aarhus C, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Levinsen