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 $^{23}$Na and Fermi $^{40}$K 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 $^{23}$Na and $D_{1}$ line for $^{40}$K. The microwave evaporation cooling is used to cool $^{23}$Na in $| F=2,m_{F}=2\rangle$ in an optically plugged magnetic trap, meanwhile, $^{40}$K in $| F=9/2,m_{F}=9/2\rangle$ is sympathetic cooled. Then the mixture is loaded into a large volume optical dipole trap where $^{23}$Na atoms are immediately transferred to $|1,1\rangle$ for further effective cooling to avoid the strong three-body loss between $^{23}$Na atoms in $|2,2\rangle$ and $^{40}$K atoms in $|9/2,9/2\rangle$. At the end of the evaporation in optical trap, a degenerate Fermi gas of $^{40}$K with 1.9$\times10^{5}$ atoms at $T/T_{F}$=0.5 in the $|9/2,9/2\rangle$ hyperfine state coexists with a Bose-Einstein condensate (BEC) of $^{23}$Na with 8$\times10^{4}$ atoms in the $|1,1\rangle$ hyperfine state at 300 nK. We also can produce the two species mixture with the tunable population imbalance by adjusting the $^{23}$Na magneto-optical trap loading time.

Optimal preparation of Bose and Fermi atomic gas mixtures of 87Rb and 40K in a crossed optical dipole trap

“…Then, the optical molasses step follows the compressed MOT (CMOT). Here, the 87 Rb atoms are cooled by the molasses of the D2 line while the 40 K atoms are applied by the gray molasses of the D1 line [25,48] shown in Fig. 1(b).…”