Realization of large ${}^{7}$Li Bose-Einstein condensates using gray molasses

The ultracold ${}^{7}$Li atoms are a good candidate for studying non-equilibrium phenomena by means of relatively light mass and the broad Feshbach resonance. In this poster, we report an apparatus that produces Bose-Einstein condensates with $ 2.7 \times 10^{6} $ atoms in 11s. To have rapid evaporation cooling in a magnetic trap, we adopt $D_{1}$ gray molasses [1] that cools atoms trapped in a magneto-optical trap to 25$\mu$K. Run-away evaporation cooling is achieved in a plugged quadrupole magnetic trap, where the Majorana atom loss is fully suppressed by a repulsive optical barrier. The BECs are obtained in a crossed-optical dipole potential by evaporation near the Feshbach resonance. For efficient evaporation, we apply a vertical field gradient, tilting the optical potential to reduce potential depth [2]. \\ [1] A. T. Grier, I. Ferrier-Barbut, B. S. Rem, M. Delehaye, L. Khaykovich, F. Chevy, and C. Salomon, Phys. Rev. A - At. Mol. Opt. Phys. 87, 1 (2013).\\ [2] C. L. Hung, X. Zhang, N. Gemelke, and C. Chin, Phys. Rev. A - At. Mol. Opt. Phys. 78, 1 (2008).