Dual-species Bose-Einstein condensates of Na23 and K41 with tunable interactions

We report the creation of dual-species Bose-Einstein condensates (BECs) of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mmultiscripts><a:mi>Na</a:mi><a:mprescripts/><a:none/><a:mn>23</a:mn></a:mmultiscripts></a:math> and <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mmultiscripts><b:mi mathvariant="normal">K</b:mi><b:mprescripts/><b:none/><b:mn>41</b:mn></b:mmultiscripts></b:math>. Favorable background scattering lengths enable efficient sympathetic cooling of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mmultiscripts><d:mi mathvariant="normal">K</d:mi><d:mprescripts/><d:none/><d:mn>41</d:mn></d:mmultiscripts></d:math> via forced evaporative cooling of <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mmultiscripts><f:mi>Na</f:mi><f:mprescripts/><f:none/><f:mn>23</f:mn></f:mmultiscripts></f:math> in a plugged magnetic trap and an optical dipole trap. The <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mn>1</g:mn><g:mo>/</g:mo><g:mi>e</g:mi></g:mrow></g:math> 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 <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mn>3</h:mn><h:mo>×</h:mo><h:msup><h:mn>10</h:mn><h:mn>5</h:mn></h:msup></h:mrow><h:mo> </h:mo><h:mmultiscripts><h:mi>Na</h:mi><h:mprescripts/><h:none/><h:mn>23</h:mn></h:mmultiscripts></h:math> atoms surrounding <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:mrow><i:mn>5</i:mn><i:mo>×</i:mo><i:msup><i:mn>10</i:mn><i:mn>4</i:mn></i:msup></i:mrow><i:mo> </i:mo><i:mmultiscripts><i:mi mathvariant="normal">K</i:mi><i:mprescripts/><i:none/><i:mn>41</i:mn></i:mmultiscripts></i:math> 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 <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mi>s</k:mi></k:math>-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 <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mrow><l:mmultiscripts><l:mi>Na</l:mi><l:mprescripts/><l:none/><l:mn>23</l:mn></l:mmultiscripts><l:mmultiscripts><l:mi mathvariant="normal">K</l:mi><l:mprescripts/><l:none/><l:mn>41</l:mn></l:mmultiscripts></l:mrow></l:math> molecules as well as the exploration of many-body physics in bosonic <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mrow><n:mmultiscripts><n:mi>Na</n:mi><n:mprescripts/><n:none/><n:mn>23</n:mn></n:mmultiscripts><n:mtext>−</n:mtext><n:mmultiscripts><n:mi mathvariant="normal">K</n:mi><n:mprescripts/><n:none/><n:mn>41</n:mn></n:mmultiscripts></n:mrow></n:math> mixtures. Published by the American Physical Society 2024