Fermi-Bose quantum degenerate 40K-87Rb mixture with attractive interaction -: art. no. 150403

We report on the achievement of simultaneous quantum degeneracy in a mixed gas of fermionic K-40 and bosonic Rb-87. Potassium is cooled to 0.3 times the Fermi temperature by means of an efficient thermalization with evaporatively cooled rubidium. Direct measurement of the collisional cross-section confirms a large interspecies attraction. This interaction is shown to affect the expansion of the Bose-Einstein condensate released from the magnetic trap, where it is immersed in the Fermi sea.