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Register a new userTunable dual-species Bose-Einstein condensates of $^{39}$K and $^{87}$Rb
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We present the production of dual-species Bose-Einstein condensates of $^{39}mathrm{K}$ and $^{87}mathrm{Rb}$. Preparation of both species in the $left| F=1,m_F=-1 rightrangle$ state enabled us to exploit a total of three Fesh-bach resonances which allows for simultaneous Feshbach tuning of the $^{39}mathrm{K}$ intraspecies and the $^{39}mathrm{K}$-$^{87}mathrm{Rb}$ interspecies scattering length. Thus dual-species Bose-Einstein condensates were produced by sympathetic cooling of $^{39}mathrm{K}$ with $^{87}mathrm{Rb}$. A dark spontaneous force optical trap was used for $^{87}mathrm{Rb}$, to reduce the losses in $^{39}mathrm{K}$ 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 $117.56(2),mathrm{G}$ and to determine the width of the resonance to $1.21(5),mathrm{G}$ by rethermalization measurements. The transition region from miscible to immiscible dual-species condensates was investigated and the interspecies background scattering length was determined to $28.5,a_mathrm{0}$ using an empirical model. This paves the way for dual-species experiments with $^{39}mathrm{K}$ and $^{87}mathrm{Rb}$ BECs ranging from molecular physics to precision metrology.
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We report the production of $^{39}$K and $^{87}$Rb Bose-Einstein condensates (BECs) in the lowest hyperfine states $| F=1,m_{F}=1 rangle$ simultaneously. We collect atoms in bright/dark magneto-optical traps (MOTs) of $^{39}$K/$^{87}$Rb to overcome the light-assisted losses of $^{39}$K atoms. Gray molasses cooling on the D1 line of the $^{39}$K is used to effectively increase the phase density, which improves the loading efficiency of $^{39}$K into the quadrupole magnetic trap. Simultaneously, the normal molasses are employed for $^{87}$Rb. After the microwave evaporation cooling on $^{87}$Rb in the optically plugged magnetic trap, the atoms mixture is transferred to a crossed optical dipole trap, where the collisional properties of the two species in different combinations of the hyperfine states are studied. The dual species BECs of $^{39}$K and $^{87}$Rb are obtained by further evaporative cooling in optical dipole trap at a magnetic field of 372.6 G with the background repulsive interspecies scattering length $a_{KRb}$ = 34 $a_{0}$ ($a_{0}$ is the Bohr radius) and the intraspecies scattering length $a_{K}$ = 20.05 $a_{0}$.
We produce a Bose-Einstein condensate of 39-K atoms. Condensation of this species with naturally small and negative scattering length is achieved by a combination of sympathetic cooling with 87-Rb and direct evaporation, exploiting the magnetic tuning of both inter- and intra-species interactions at Feshbach resonances. We explore tunability of the self-interactions by studying the expansion and the stability of the condensate. We find that a 39-K condensate is interesting for future experiments requiring a weakly interacting Bose gas.
We describe a simple and compact single-chamber apparatus for robust production of $^87$Rb Bose-Einstein condensates. The apparatus is built from off-the-shelf components and allows production of quasi-pure condensates of > $3times 10^5$ atoms in < 30 s. This is achieved using a hybrid trap created by a quadrupole magnetic field and a single red-detuned laser beam [Y.-J. Lin et al., Phys. Rev. A 79, 063631 (2009)]. In the same apparatus we also achieve condensation in an optically plugged quadrupole trap [K. B. Davis et al., Phys. Rev. Lett. 75, 3969 (1995)] and show that as little as 70 mW of plug-laser power is sufficient for condensation, making it viable to pursue this approach using inexpensive diode lasers. While very compact, our apparatus features sufficient optical access for complex experiments, and we have recently used it to demonstrate condensation in a uniform optical-box potential [A. Gaunt et al., arXiv:1212.4453 (2012)].
We report the formation of a dual-species Bose-Einstein condensate of $^{87}$Rb and $^{133}$Cs in the same trapping potential. Our method exploits the efficient sympathetic cooling of $^{133}$Cs via elastic collisions with $^{87}$Rb, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to $2times10^{4}$ atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the $^{87}$Rb during the cooling, we create single species $^{133}$Cs condensates of up to $6times10^{4}$ atoms.
We investigate the mean--field equilibrium solutions for a two--species immiscible Bose--Einstein condensate confined by a harmonic confinement with additional linear perturbations. We observe a range of equilibrium density structures, including `ball and shell formations and axially/radially separated states, with a marked sensitivity to the potential perturbations and the relative atom number in each species. Incorporation of linear trap perturbations, albeit weak, are found to be essential to match the range of equilibrium density profiles observed in a recent Rb-87 - Cs-133 Bose-Einstein condensate experiment [D. J. McCarron et al., Phys. Rev. A, 84, 011603(R) (2011)]. Our analysis of this experiment demonstrates that sensitivity to linear trap perturbations is likely to be important factor in interpreting the results of similar experiments in the future.
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