Observation of Heteronuclear Feshbach Resonances in a Mixture of Bosons and Fermions

Three magnetic-field induced heteronuclear Feshbach resonances were identified in collisions between bosonic ⁸⁷Rb and fermionic ⁴⁰K atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and 543±2  G. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding (-281±15)a₀ and (-54±12)a₀, respectively. The width of the loss feature at 543 G is 3.7±1.5  G wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.