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arXiv:2003.13362 · Condensed Matter

A Dual-Species Bose-Einstein Condensate with Attractive Interspecies Interactions

Alessia Burchianti, Chiara D’Errico, Marco Prevedelli, Luca Salasnich, Francesco Ancilotto, Michele Modugno, Francesco Minardi, Chiara Fort

Published Mar 21, 2020• 54 citations
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Abstract

We report on the production of a 41 K- 87 Rb dual-species Bose–Einstein condensate with tunable interspecies interaction and we study the mixture in the attractive regime; i.e., for negative values of the interspecies scattering length a 12 . The binary condensate is prepared in the ground state and confined in a pure optical trap. We exploit Feshbach resonances for tuning the value of a 12 . After compensating the gravitational sag between the two species with a magnetic field gradient, we drive the mixture into the attractive regime. We let the system evolve both in free space and in an optical waveguide. In both geometries, for strong attractive interactions, we observe the formation of self-bound states, recognizable as quantum droplets. Our findings prove that robust, long-lived droplet states can be realized in attractive two-species mixtures, despite the two atomic components possibly experiencing different potentials.

DOI
10.3390/condmat5010021

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Dual-species Bose-Einstein condensates of 23^{23}23Na and 41^{41}41K with tunable interactions
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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 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
We report the formation of a dual-species Bose-Einstein condensate of 87Rb^{87}\mathrm{Rb}87Rb and 133Cs^{133}\mathrm{Cs}133Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of 133Cs^{133}\mathrm{Cs}133Cs via elastic collisions with 87Rb^{87}\mathrm{Rb}87Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the 87Rb^{87}\mathrm{Rb}87Rb during the cooling, we create single-species 133Cs^{133}\mathrm{Cs}133Cs condensates of up to $6\ifmmode\times\else\texttimes\fi{}{10}^{4}$ atoms.