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arXiv:cond-mat/0703714 · Physical Review Letters

K39 Bose-Einstein Condensate with Tunable Interactions

G. Roati, Matteo Zaccanti, Chiara D’Errico, Jacopo Catani, Michele Modugno, Andrea Simoni, M. Inguscio, Giovanni Carlo Modugno

Published Jul 6, 2007• 239 citations
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Abstract

We produce a Bose-Einstein condensate of 39K atoms. Condensation of this species with a naturally small and negative scattering length is achieved by a combination of sympathetic cooling with 87Rb and direct evaporation, exploiting the magnetic tuning of both inter- and intraspecies interactions at Feshbach resonances. We explore the tunability of the self-interactions by studying the expansion and the stability of the condensate. We find that a 39K condensate is interesting for future experiments requiring a weakly-interacting Bose gas.

DOI
10.1103/physrevlett.99.010403

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We produce a Bose-Einstein condensate of 39K atoms. Condensation of this species with a naturally small and negative scattering length is achieved by a combination of sympathetic cooling with 87Rb and direct evaporation, exploiting the magnetic tuning of both inter- and intraspecies interactions at Feshbach resonances. We explore the tunability of the self-interactions by studying the expansion and the stability of the condensate. We find that a 39K condensate is interesting for future experiments requiring a weakly-interacting Bose gas.
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We report the all-optical production of Bose-Einstein condensates (BEC) of 39K^{39}\mathrm{K}39K atoms. We directly load $3\ifmmode\times\else\texttimes\fi{}{10}^{7}$ atoms in a large volume optical dipole trap from gray molasses on the D1 transition. We then apply a small magnetic quadrupole field to polarize the sample before transferring the atoms in a tightly confining optical trap. Evaporative cooling is finally performed close to a Feshbach resonance to enhance the scattering length. Our setup allows one to cross the BEC threshold with $3\ifmmode\times\else\texttimes\fi{}{10}^{5}$ atoms every 7 s. As an illustration of the interest of the tunability of the interactions we study the expansion of Bose-Einstein condensates in the one-dimensional to three-dimensional crossover.
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.
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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