Towards the Bose-Einstein condensation of NaRb molecules

Recent years have witnessed tremendous progress in creating and manipulating ground-state ultracold polar molecules. However, the rapid loss regardless of the chemical reactivities is still a hurdle for many future explorations. Microwave shielding has been proved to be a viable method to suppress the loss. In our system of non-reactive bosonic NaRb molecules, we have achieved a long-lived sample after suppressing the two-body loss by two orders of magnitude with a circularly polarized microwave blue detuned to the rotational transition and demonstrated effective evaporation cooling in selected parameter regimes [1]. However, due to the field-linked states caused by the dipolar interaction, further improvement of evaporation toward a BEC requires understanding and suppression of loss processes beyond two body. Here, we report our progress in controlling the molecule-molecule collisions with the double microwave dressing method [2] by applying simultaneously a σ⁺ and a π polarized microwave fields to eliminate the field-linked states. The prospects for achieving a BEC of NaRb molecules will also be presented.