Broad Feshbach Resonance in the 6Li-40K Mixture

We study the widths of interspecies Feshbach resonances in a mixture of the fermionic quantum gases Li-6 and K-40. We develop a model to calculate the width and position of all available Feshbach resonances for a system. Using the model, we select the optimal resonance to study the Li-6/K-40 mixture. Experimentally, we obtain the asymmetric Fano line shape of the interspecies elastic cross section by measuring the distillation rate of Li-6 atoms from a potassium-rich Li-6/K-40 mixture as a function of magnetic field. This provides us with the first experimental determination of the width of a resonance in this mixture, Delta B = 1.5(5) G. Our results offer good perspectives for the observation of universal crossover physics using this mass-imbalanced fermionic mixture.