We use $D_1$ gray molasses to achieve Bose-Einstein condensation of a large number of ${}^{41}\mathrm{K}$ atoms in an optical dipole trap. By combining a specific configuration of a compressed magneto-optical trap with $D_1$ gray molasses, we obtain a cold sample of $2.4\times {10}^9$ atoms with a temperature as low as 42 $\mu \mathrm{K}$. After magnetically transferring the atoms into the final glass cell, we perform a two-stage evaporative cooling. A condensate with up to $1.2\times {10}^6$ atoms in the lowest Zeeman state $|F=1,m_F=1\rangle$ is achieved in the optical dipole trap. Furthermore, we observe two narrow Feshbach resonances in the lowest hyperfine channel, which are in good agreement with theoretical predictions.

• Received 12 June 2016

DOI:https://doi.org/10.1103/PhysRevA.94.033408