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A: Fachverband Atomphysik
A 25: Ultracold Atoms and Molecules I (joint session Q/A)
A 25.2: Talk
Thursday, March 17, 2022, 10:45–11:00, Q-H10
Rapid generation of all-optical 39K Bose-Einstein condensates — •Alexander Herbst, Henning Albers, Vera Vollenkemper, Knut Stolzenberg, Sebastian Bode, and Dennis Schlippert — Institute of Quantum Optics, Leibniz University Hannover, Welfengarten 1, 30167 Hannover, Germany
Ultracold potassium is a promising candidate for fundamental research and quantum sensing applications as it offers multiple broad Feshbach resonances at small magnetic fields. These can be used to control the atomic scattering length and therefore allow, e.g., for the suppression of phase diffusion or the generation of solitons. To apply this technique the magnetic field must be kept as an external degree of freedom thus necessitating optical trapping. However, compared to their magnetic counterparts, optical traps suffer from slower evaporative cooling. This poses a major challenge if the experiment requires a high repetition rate. We investigate the production of all-optical 39K BECs under different scattering lengths in a time-averaged crossed optical dipole trap. By tuning the scattering length in a range between 75 a0 and 350 a0 we demonstrate a trade off between evaporation speed and final atom number and decrease our evaporation time by a factor of five while approximately doubling the atomic flux. To this end, we are able to produce fully condensed ensembles with 5×104 atoms within 850 ms evaporation time at a scattering length of 234 a0 and 1.5× 105 atoms within 4 s at 160 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.