Production of large $^{41}$K Bose-Einstein condensates using D1 gray   molasses
  We use D1 gray molasses to achieve Bose-Einstein condensation of a large number of $^{41}$K atoms in an optical dipole trap. By combining a new configuration of compressed-MOT with D1 gray molasses, we obtain a cold sample of $2.4\times10^9$ atoms with a temperature as low as 42 $\mu$K. After magnetically transferring the atoms into the final glass cell, we perform a two-stage evaporative cooling. A condensate with up to $1.2\times10^6$ 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. 
Hao-Ze Chen, Xing-Can Yao, Yu-Ping Wu, Xiang-Pei Liu, Xiao-Qiong Wang,   Yu-Xuan Wang, Yu-Ao Chen, and Jian-Wei Pan
cond-mat.quant-gas physics.atom-ph