Hybrid Evaporative Cooling Of Cs-133 Atoms To Bose-Einstein Condensation

The Bose-Einstein condensation (BEC) of Cs-133 atoms offers an appealing platform for studying the many-body physics of interacting Bose quantum gases, owing to the rich Feshbach resonances that can be readily achieved in the low magnetic field region. However, it is notoriously difficult to cool Cs-133 atoms to their quantum degeneracy. Here we report a hybrid evaporative cooling of Cs-133 atoms to BEC. Our approach relies on a combination of the magnetically tunable evaporation with the optical evaporation of atoms in a magnetically levitated optical dipole trap overlapping with a dimple trap. The magnetic field gradient is reduced for the magnetically tunable evaporation. The subsequent optical evaporation is performed by lowering the depth of the dimple trap. We study the dependence of the peak phase space density (PSD) and temperature on the number of atoms during the evaporation process, as well as how the PSD and atom number vary with the trap depth. The results are in excellent agreement with the equation model for evaporative cooling. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement