Rapid generation of all-optical $^{39}$K Bose-Einstein condensates using a low-field Feshbach resonance

Abstract

Ultracold potassium is a promising candidate for quantum technological applications as it allows changing intra-atomic interactions via low-field magnetic Feshbach resonances. However, the realization of high-flux sources of Bose-Einstein condensates remains challenging due to the necessity of optical trapping to use a Feshbach resonance. We investigate the production of all-optical 39 K Bose-Einstein condensates under different scattering lengths using a low-field Feshbach resonance near 33 G. By tuning the scattering length in a range between 75 a0 and 300 a0 we demonstrate a trade off between evaporation speed and final atom number and decrease our evaporation time by a factor of 5 while approximately doubling the atomic flux. To this end, we are able to produce fully condensed ensembles with 5 × 10 4 atoms within 850 ms evaporation time at a scattering length of 232 a0 and 1.6 × 10 5 atoms within 4 s at 158 a0, respectively. We analyze the flux scaling with respect to collision rates and describe routes towards high-flux sources of ultra-cold potassium for inertial sensing.