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

We report the production of ³⁹K and ⁸⁷Rb Bose–Einstein condensates (BECs) in the lowest hyperfine states | F = 1,m_F = 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 a₀ (a₀ is the Bohr radius) and the intraspecies scattering length a_K = 20.05a₀. [ABSTRACT FROM AUTHOR]