Boson-fermion mixtures in two-color optical dipole traps.

We propose the use of a combined optical dipole trap to achieve Fermi degeneracy by sympathetic cooling with a different bosonic species. Two far-detuned pairs of laser beams focused on the atomic clouds are used to confine the two atomic species with different trapping strengths. We show that a deep Fermi degeneracy regime can be potentially achieved earlier than Bose-Einstein condensation, as discussed in the favorable situation of a {sup 6}L i-{sup 23}Na mixture. This opens up the possibility of experimentally investigating a mixture of superfluid Fermi and normal Bose gases