The Physics of Type-II MOTs

Magneto-Optical Traps (MOTs) are a useful tool for quantum science. However, high phase space densities are necessary for creating good conditions to begin evaporative cooling. It has been recently shown that type-II transitions generally achieving higher densities than the typical type-I transitions. In this work, we demonstrate the ability to trap and cool a sample of ~200 million Cs atoms by first trapping in a type-I MOT and then flipping the magnetic field gradient and changing the laser frequencies to trap in a type-II MOT. We achieve axial and radial temperatures of 15(1) and 12.6(1) uK. We also report progress toward type-II MOTs for Li. Trapping Li a type-II MOT will allow us to achieve higher phase space densities than attainable in a traditional type-I Li MOT due to sub-Doppler cooling and reduced scattering. We expect this to allow us to load novel optical trap geometries for quantum simulation experiments.