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

Abstract

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,mF = 2〉 in an optically plugged magnetic trap, meanwhile, 40K in | F = 9/2,mF = 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 × 105 atoms at T/TF = 0.5 in the |9/2,9/2〉 hyperfine state coexists with a Bose–Einstein condensate (BEC) of 23Na with 8 × 104 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.