Dual-species Bose-Einstein condensates of ${}^{23}$Na and ${}^{41}$K with tunable interactions

Abstract

We report the creation of dual-species Bose-Einstein condensates (BECs) of ${}^{23}$Na and ${}^{41}$K. Favorable background scattering lengths enable efficient sympathetic cooling of ${}^{41}$K via forced evaporative cooling of ${}^{23}$Na in a plugged magnetic trap and an optical dipole trap. The $1/e$ lifetime of the thermal mixture in the stretched hyperfine state exceeds 5 s in the presence of background scattering. At the end of evaporation, we create dual BECs in the immiscible phase, with about $3\times 10^5$ ${}^{23}$Na atoms surrounding $5\times 10^4$ ${}^{41}$K atoms. To further enable the tuning of the interspecies interaction strength, we locate multiple Feshbach resonances at magnetic fields up to 100 G. The broadest $s$-wave resonance located at 73.4(3) G features a favorable width of 1.8(2) G. This work sets the stage for the creation of ultracold gases of strongly dipolar bosonic ${}^{23}$Na${}^{41}$K molecules as well as the exploration of many-body physics in bosonic ${}^{23}$Na-${}^{41}$K mixtures.

6 pages, 4 figures