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 $3\times10^5$ $^{23}$Na atoms surrounding $5\times10^4$ $^{41}$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.