Quantum degenerate Bose-Fermi atomic gas mixture of ²³Na and ⁴⁰K

We report a compact experimental setup for producing a quantum degenerate mixture of Bose ²³Na and Fermi ⁴⁰K gases. The atoms are collected in dual dark magneto–optical traps (MOT) with species timesharing loading to reduce the light-induced loss, and then further cooled using the gray molasses technique on the D ₂ line for ²³Na and D ₁ line for ⁴⁰K. The microwave evaporation cooling is used to cool ²³Na in | F = 2, m _F = 2〉 in an optically plugged magnetic trap, meanwhile, ⁴⁰K in | F = 9/2, m _F = 9/2〉 is sympathetically cooled. Then the mixture is loaded into a large volume optical dipole trap where ²³Na atoms are immediately transferred to |1,1〉 for further effective cooling to avoid the strong three-body loss between ²³Na atoms in |2,2〉 and ⁴⁰K atoms in |9/2,9/2〉. At the end of the evaporation in optical trap, a degenerate Fermi gas of ⁴⁰K with 1.9 × 10 ⁵ atoms at T/ T _F = 0.5 in the |9/2,9/2〉 hyperfine state coexists with a Bose–Einstein condensate (BEC) of ²³Na with 8 × 10 ⁴ atoms in the |1,1〉 hyperfine state at 300 nK. We also can produce the two species mixture with the tunable population imbalance by adjusting the ²³Na magneto–optical trap loading time.