Fermion-mediated interactions and binding of bosons in a Cs–Li Bose-Fermi mixture

Ultracold Bose–Fermi mixtures provide a versatile platform for studying how a many-body environment modifies interactions and binding between a small number of particles. In such systems, the presence of a degenerate Fermi gas can qualitatively alter the effective interactions experienced by immersed bosons, leading to emergent few-body phenomena that have no counterpart in isolated systems. Here we investigate a strongly interacting mixture of bosonic Cs-133 and fermionic Li-6 atoms. By tuning the boson–fermion interaction close to resonance, we observe that the surrounding Fermi gas induces an effective attraction between bosons, resulting in the appearance of a two-body binding resonance within the bosonic sector. In addition, we find that the fermionic medium modifies the locations of bosonic few-body resonances, indicating a strong coupling between few-body bound states and the many-body background. Our results demonstrate how many-body effects originating from the degenerate Fermi gas can strongly influence few-body bound-state formation.