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.