Feshbach spectroscopy of a $\mathrm{K}\text{−}\mathrm{Rb}$ atomic mixture

We perform extensive magnetic Feshbach spectroscopy of an ultracold mixture of fermionic ${}^{40}\mathrm{K}$ and bosonic ${}^{87}\mathrm{Rb}$ atoms. The magnetic-field locations of 13 interspecies resonances are used to construct a quantum collision model able to predict accurate collisional parameters for all $\mathrm{K}\text{−}\mathrm{Rb}$ isotopic pairs. In particular, we determine the interspecies $s$-wave singlet and triplet scattering lengths for the ${}^{40}\mathrm{K}\text{−}{}^{87}\mathrm{Rb}$ mixture as $(-108\pm 3)a_0$ and $(-205\pm 5)a_0$, respectively. We also predict accurate scattering lengths and the position of Feshbach resonances for the other $\mathrm{K}\text{−}\mathrm{Rb}$ isotopic pairs. We discuss the consequences of our results for current and future experiments with ultracold $\mathrm{K}\text{−}\mathrm{Rb}$ mixtures.

Figure 1

Relative inelastic losses of potassium atoms in a ${}^{40}\mathrm{K}\text{−}{}^{87}\mathrm{Rb}$ mixture in its absolute ground state at interspecies Feshbach resonances. The two features near 455 and $514\mathrm{G}$ are $p$-wave resonances, the others are $s$-wave resonances.