Production of large $^{41}$K Bose-Einstein condensates using D1 gray molasses

TL;DR

This paper reports the production of large $^{41}$K Bose-Einstein condensates using D1 gray molasses, achieving high atom numbers and low temperatures, and identifying Feshbach resonances.

Contribution

The study introduces a new configuration combining compressed-MOT with D1 gray molasses for efficient Bose-Einstein condensation of $^{41}$K.

Findings

Achieved Bose-Einstein condensates with up to 1.2 million atoms.

Produced a cold sample of 2.4 billion atoms at 42 μK.

Observed two narrow Feshbach resonances matching theoretical predictions.

Abstract

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.