Rapid production of large $^{7}$Li Bose-Einstein condensates using $D_1$ gray molasses

Abstract

We demonstrate the production of large $^7$Li Bose-Einstein condensates in an optical dipole trap using $D_1$ gray molasses. The sub-Doppler cooling technique reduces the temperature of $4\times10^9$ atoms to $25~\mu{}$K in 3~ms. After microwave evaporation cooling in a magnetic quadrupole trap, we transfer the atoms to a crossed optical dipole trap, where we employ a magnetic Feshbach resonance on the $|F=1,m_F=1\rangle$ state. Fast evaporation cooling is achieved by tilting the optical potential using a magnetic field gradient on the top of the Feshbach field. Our setup produces pure condensates with $2.7\times10^6$ atoms in the optical potential for every 11~s. The trap tilt evaporation allows rapid thermal quench, and spontaneous vortices are observed in the condensates as a result of the Kibble-Zurek mechanism.