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 ${}^{87}\mathrm{R}\mathrm{b}$ and fermionic ${}^{40}\mathrm{K}$ atoms in their absolute ground states. Strong inelastic loss from an optically trapped mixture was observed at the resonance positions of 492, 512, and $543\pm 2\mathrm{G}$. The magnetic-field locations of these resonances place a tight constraint on the triplet and singlet cross-species scattering lengths, yielding $(-281\pm 15)a_0$ and $(-54\pm 12)a_0$, respectively. The width of the loss feature at 543 G is $3.7\pm 1.5\mathrm{G}$ wide; this broad Feshbach resonance should enable experimental control of the interspecies interactions.