Heating Reduction in a Shaken Optical Lattice by Modifying Lattice Beam Profile

A lithium molecular Bose-Einstein condensate loaded into an optical lattice can evolve into states with quantized momentum due to the strong periodic potential, as described by the Kapitza-Dirac (KD) scattering effect. When a time-periodic modulation is applied to the retro-reflected beam, the wave packets can bifurcate into two clusters in real space as a result of the modified band dispersion [1]. We learn that the success of this bifurcation depends on the cleanliness of the lattice beam profile. By placing an iris along the beam path, we blocked the outer rings and approximated a clean Gaussian profile. Further investigation showed that while the beam profile does not affect KD scattering at the same lattice depth, it can reduce the heating of atoms during shaken lattice experiments. Additionally, we compared the results of our shaken lattice experiments with different beam sizes at a constant lattice depth.

[1] Wang, K. et al. (2023) ‘Instability and momentum bifurcation of a molecular Bose-Einstein condensate in a shaken lattice with exotic dispersion’, Physical Review A, 108(5). doi:10.1103/physreva.108.l051302.