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

Abstract

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 Bohr radius) and the intraspecies scattering length a K = 20.05a 0.