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arXiv:1003.4819 · Review of Scientific Instruments

R 85 b tunable-interaction Bose–Einstein condensate machine

P. A. Altin, Nicholas P. Robins, D. Döring, J. E. Debs, Rachel Poldy, C. Figl, J. D. Close

Published Jun 1, 2010• 40 citations
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Abstract

We describe our experimental setup for creating stable Bose-Einstein condensates (BECs) of (85)Rb with tunable interparticle interactions. We use sympathetic cooling with (87)Rb in two stages, initially in a tight Ioffe-Pritchard magnetic trap and subsequently in a weak, large-volume, crossed optical dipole trap, using the 155 G Feshbach resonance to manipulate the elastic and inelastic scattering properties of the (85)Rb atoms. Typical (85)Rb condensates contain 4 x 10(4) atoms with a scattering length of a=+200a(0). Many aspects of the design presented here could be adapted to other dual-species BEC machines, including those involving degenerate Fermi-Bose mixtures. Our minimalist apparatus is well suited to experiments on dual-species and spinor Rb condensates, and has several simplifications over the (85)Rb BEC machine at JILA, which we discuss at the end of this article.

DOI
10.1063/1.3430538

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We describe our experimental setup for creating stable Bose-Einstein condensates (BECs) of (85)Rb with tunable interparticle interactions. We use sympathetic cooling with (87)Rb in two stages, initially in a tight Ioffe-Pritchard magnetic trap and subsequently in a weak, large-volume, crossed optical dipole trap, using the 155 G Feshbach resonance to manipulate the elastic and inelastic scattering properties of the (85)Rb atoms. Typical (85)Rb condensates contain 4 x 10(4) atoms with a scattering length of a=+200a(0). Many aspects of the design presented here could be adapted to other dual-species BEC machines, including those involving degenerate Fermi-Bose mixtures. Our minimalist apparatus is well suited to experiments on dual-species and spinor Rb condensates, and has several simplifications over the (85)Rb BEC machine at JILA, which we discuss at the end of this article.
Abstract We have realized a dual-species Bose–Einstein condensate (BEC) of 23 Na and 87 Rb atoms and observed its immiscibility. Because of the favorable background intra- and inter-species scattering lengths, stable condensates can be obtained via efficient evaporative cooling and sympathetic cooling without the need for fine tuning of the interactions. Our system thus provides a clean platform for studying inter-species interactions–driven effects in superfluid mixtures. With a Feshbach resonance, we have successfully created double BECs with largely tunable inter-species interactions and studied the miscible–immiscible phase transition.
We report the creation of dual-species Bose-Einstein condensates (BECs) of Na23 and K41 . Favorable background scattering lengths enable efficient sympathetic cooling of K41 via forced evaporative cooling of Na23 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 3×105 Na23 atoms surrounding 5×104 K41 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 Na23K41 molecules as well as the exploration of many-body physics in bosonic Na23−K41 mixtures. Published by the American Physical Society 2024
Dual-species Bose-Einstein condensates of 23^{23}23Na and 41^{41}41K with tunable interactions
We report the creation of dual-species Bose-Einstein condensates (BECs) of 23^{23}23Na and 41^{41}41K. Favorable background scattering lengths enable efficient sympathetic cooling of 41^{41}41K via forced evaporative cooling of 23^{23}23Na in a plugged magnetic trap and an optical dipole trap. The 1/e1/e1/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 3×1053\times10^53×105 23^{23}23Na atoms surrounding 5×1045\times10^45×104 41^{41}41K 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 sss-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^{23}23Na41^{41}41K molecules as well as the exploration of many-body physics in bosonic 23^{23}23Na-41^{41}41K mixtures.
A 23^{23}23Na and 87^{87}87Rb double Bose-Einstein condensate with tunable interactions
We have realized a dual-species Bose-Einstein condensate of 23^{23}23Na and 87^{87}87Rb atoms and observed their immiscibility. Because of the favorite background intra- and inter-species scattering lengths, evaporative cooling and sympathetic cooling are efficient without the need for fine controlling of the interactions. Our system thus provides a clean platform for studying quantum fluid mixtures with tunable inter-species interactions. We have also demonstrated the interaction tuning with a inter-species Feshbach resonance by investigating the elastic collisions near zero crossing of the Na-Rb scattering length.
We present the production of dual-species Bose-Einstein condensates (BECs) of 39K^{39}\mathrm{K}39K and 87Rb^{87}\mathrm{Rb}87Rb. Preparation of both species in the $\left|F=1,{m}_{F}=\ensuremath{-}1\right\ensuremath{\rangle}$ state enabled us to exploit a total of three Feshbach resonances, which allows for simultaneous Feshbach tuning of the 39K^{39}\mathrm{K}39K intraspecies and the $^{39}\mathrm{K}\text{\ensuremath{-}}^{87}\mathrm{Rb}$ interspecies scattering length. Thus dual-species Bose-Einstein condensates were produced by sympathetic cooling of 39K^{39}\mathrm{K}39K with 87Rb^{87}\mathrm{Rb}87Rb. A dark spontaneous force optical trap was used for 87Rb^{87}\mathrm{Rb}87Rb to reduce the losses in 39K^{39}\mathrm{K}39K due to light-assisted collisions in the optical trapping phase, which can be of benefit for other dual-species experiments. The tunability of the scattering length was used to perform precision spectroscopy of the interspecies Feshbach resonance located at 117.56(2) G and to determine the width of the resonance to 1.21(5) G by rethermalization measurements. The transition region from miscible to immiscible dual-species condensates was investigated and the interspecies background scattering length was determined to 28.5a028.5{a}_{0}28.5a0​ using an empirical model. This paves the way for dual-species experiments with 39K^{39}\mathrm{K}39K and 87Rb^{87}\mathrm{Rb}87Rb BECs ranging from molecular physics to precision metrology.
We describe an experimental setup and the cooling procedure for producing 39K^{39}\mathrm{K}39K Bose-Einstein condensates of over $4\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms. Condensation is achieved via a combination of sympathetic cooling with 87Rb^{87}\mathrm{Rb}87Rb in a quadrupole-Ioffe-configuration (QUIC) magnetic trap and direct evaporation in a large-volume crossed optical dipole trap, where we exploit the broad Feshbach resonance at 402 G to tune the 39K^{39}\mathrm{K}39K interactions from weak and attractive to strong and repulsive. In the same apparatus we create quasipure 87Rb^{87}\mathrm{Rb}87Rb condensates of over $8\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms.