Tunable Fujita-Miyazawa-type three-body force in ultracold atoms

We show how a Fujita-Miyazawa-type three-body force emerges among three impurity atoms immersed in an atomic Bose-Einstein condensate near an interspecies Feshbach resonance. As a result of thermal average over excitations in the medium and impurities as well as expansion with respect to the impurity-medium and Feshbach resonance couplings, two superfluid phonons and a closed channel resonance play a role in producing an effective three-body force, as in the original three-nucleon case in which two pions and a $Δ$ resonance are involved. The proposed Fujita-Miyazawa-type three-body force can be enhanced by tuning the closed-channel energy level via an external magnetic field, and moreover, its strength can be confirmed experimentally by measuring the impurity equation of state. Our result gives a new insight into an analogy between atomic polarons and nuclear few-body systems.