Dual-species Bose-Einstein condensate of K41 and Rb87 in a hybrid trap (original) (raw)

Production of dual species Bose–Einstein condensates of 39K and 87Rb*

Chinese Physics B, 2021

We report the production of 39K and 87Rb Bose–Einstein condensates (BECs) in the lowest hyperfine states | F = 1,mF = 1 〉 simultaneously. We collect atoms in bright/dark magneto-optical traps (MOTs) of 39K/87Rb to overcome the light-assisted losses of 39K atoms. Gray molasses cooling on the D1 line of the 39K is used to effectively increase the phase density, which improves the loading efficiency of 39K into the quadrupole magnetic trap. Simultaneously, the normal molasses is employed for 87Rb. After the microwave evaporation cooling on 87Rb 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 39K and 87Rb are obtained by further evaporative cooling in an 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 ...

Rubidium-87 Bose-Einstein condensate in an optically plugged quadrupole trap

Physical Review A, 2012

We describe an experiment to produce 87 Rb Bose-Einstein condensates in an optically plugged magnetic quadrupole trap, using a blue-detuned laser. Due to the large detuning of the plug laser with respect to the atomic transition, the evaporation has to be carefully optimized in order to efficiently overcome the Majorana losses. We provide a complete theoretical and experimental study of the trapping potential at low temperatures and show that this simple model describes well our data. In particular we demonstrate methods to reliably measure the trap oscillation frequencies and the bottom frequency, based on periodic excitation of the trapping potential and on radio-frequency spectroscopy, respectively. We show that this hybrid trap can be operated in a well controlled regime that allows a reliable production of degenerate gases.

Simple method for generating Bose-Einstein condensates in a weak hybrid trap

Physical Review A, 2011

We report on a simple novel trapping scheme for the generation of Bose-Einstein condensates of 87 Rb atoms. This scheme employs a near-infrared single beam optical dipole trap combined with a weak magnetic quadrupole field as used for magneto-optical trapping to enhance the confinement in axial direction. Efficient forced evaporative cooling to the phase transition is achieved in this weak hybrid trap via reduction of the laser intensity of the optical dipole trap at constant magnetic field gradient.

Tunable dual-species Bose-Einstein condensates ofK39andRb87

Physical Review A, 2015

We present the production of dual-species Bose-Einstein condensates of 39 K and 87 Rb. Preparation of both species in the |F = 1, mF = −1 state enabled us to exploit a total of three Feshbach resonances which allows for simultaneous Feshbach tuning of the 39 K intraspecies and the 39 K-87 Rb interspecies scattering length. Thus dual-species Bose-Einstein condensates were produced by sympathetic cooling of 39 K with 87 Rb. A dark spontaneous force optical trap was used for 87 Rb, to reduce the losses in 39 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) 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 28.5 a0 using an empirical model. This paves the way for dual-species experiments with 39 K and 87 Rb BECs ranging from molecular physics to precision metrology.

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

Condensed Matter

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.

A compact single-chamber apparatus for Bose-Einstein condensation of 87^ 8787 Rb

2012

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 > 3 × 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)]; we 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)].

Two-component dipolar Bose-Einstein condensate in concentrically coupled annular traps

Scientific reports, 2015

Dipolar Bosonic atoms confined in external potentials open up new avenues for quantum-state manipulation and will contribute to the design and exploration of novel functional materials. Here we investigate the ground-state and rotational properties of a rotating two-component dipolar Bose-Einstein condensate, which consists of both dipolar bosonic atoms with magnetic dipole moments aligned vertically to the condensate and one without dipole moments, confined in concentrically coupled annular traps. For the nonrotational case, it is found that the tunable dipolar interaction can be used to control the location of each component between the inner and outer rings, and to induce the desired ground-state phase. Under finite rotation, it is shown that there exists a critical value of rotational frequency for the nondipolar case, above which vortex state can form at the trap center, and the related vortex structures depend strongly on the rotational frequency. For the dipolar case, it is f...

Optically plugged quadrupole trap for Bose-Einstein condensates

Physical Review A, 2005

We created sodium Bose-Einstein condensates in an optically plugged quadrupole magnetic trap (OPT). A focused, 532nm laser beam repelled atoms from the coil center where Majorana loss is significant. We produced condensates of up to 3 × 10 7 atoms, a factor of 60 improvement over previous work [1], a number comparable to the best all-magnetic traps, and transferred up to 9 × 10 6 atoms into a purely optical trap. Due to the tight axial confinement and azimuthal symmetry of the quadrupole coils, the OPT shows promise for creating Bose-Einstein condensates in a ring geometry.

The physics of trapped dilute-gas Bose–Einstein condensates

Physics Reports, 1998

Contents 1. Introduction 4 1.1. The experiments 4 1.2. The theory 7 1.3. Outline 7 2. Ground state properties of dilute-gas Bose-Einstein condensates in traps 8 2.1. Hamiltonian: binary collision model 8 2.2. Mean-field theory 9 2.3. Ground state properties of a condensate with repulsive interactions 10 2.4. Ground state properties of a condensate with attractive interactions 14 2.5. Vortex states 16 2.6. Condensate lifetime 18 2.7. Binary mixtures of Bose-Einstein condensates 19 2.8. Beyond mean-field theory: quantum properties of trapped condensates 20 3. Elementary excitations of a trapped Bose-Einstein condensate 29 3.1. Collective excitations of a trapped Bose-Einstein condensate (at ¹"0) 30 3.2. Propagation of sound in a Bose-Einstein condensate 34 3.3. Decay of collective excitations 35 3.4. Collective excitations of trapped double condensates 36 3.5. Finite temperature excitations 37 4. Light scattering from a Bose-Einstein condensate 40 4.1. Coherent light scattering 40 4.2. Incoherent light scattering 42 4.3. Manipulation of the scattering length via light scattering 47 4.4. Nonlinear atom optics 47 4.5. Interaction with quantised cavity radiation fields 48 5. Broken gauge symmetry in pairs of condensates 48 5.1. Interference of two Bose-Einstein condensates and measurement-induced phase 48 5.2. Collapses and revivals of the interference pattern visibility 54 5.3. Pumping of twin-trap condensates 55 5.4. Detection of broken gauge symmetry via light scattering 56 5.5. Pumping of double condensates via light scattering 58 5.6. Establishment of relative phase via light scattering 59 6. Quantum dynamics of a Bose-Einstein condensate in a double-well potential 60 6.1. Coherent quantum tunnelling 60 6.2. Quantum phase between tunnelling Bose-Einstein condensates 62 7. The atom laser 63 7.1. What is an ''atom laser"? 6 3 7.2. Proposed models 64 7.3. An atom laser based on evaporative cooling 65 7.4. An atom laser based on optical cooling 68 7.5. Output couplers for Bose-Einstein condensates 70 7.6. Higher-order coherence of Bose-Einstein condensates 71 8. Conclusions 72 Appendix A. Bose-Einstein condensation in a weakly interacting gas: Bogoliubov theory 73 A.1. Elimination of the condensate mode 74 A.2. Bogoliubov transformation 74 References 76

Direct evaporative cooling of ^{39}K atoms to Bose-Einstein condensation

Physical Review A, 2012

We report the realization of Bose-Einstein condensate of 39 K atoms without the aid of an additional atomic coolant. Our route to Bose-Einstein condensation comprises sub-Doppler laser cooling of large atomic clouds with more than 10 10 atoms and evaporative cooling in an optical dipole trap where the collisional cross section can be increased using magnetic Feshbach resonances. Large condensates with almost 10 6 atoms can be produced in less than 15 seconds. Our achievements eliminate the need for sympathetic cooling with Rb atoms which was the usual route implemented till date due to the unfavorable collisional property of 39 K. Our findings simplify the experimental setup for producing Bose-Einstein condensates of 39 K atoms with tunable interactions, which have a wide variety of promising applications including atom-interferometry to studies on the interplay of disorder and interactions in quantum gases.