Microwave Shielding of Bosonic NaRb Molecules

Recent years have witnessed tremendous progress in creating and manipulating ground-state ultracold polar molecules. However, the two-body loss regardless of the chemical reactivities is still a hurdle for many future explorations. Here, we investigate the loss suppression of nonreactive bosonic 23Na87Rb molecules with a circularly polarized microwave blue detuned to the rotational transition. We achieve suppression of the loss by 2 orders of magnitude with the lowest two-body loss rate coefficient reduced to 3 x 10-12 cm3/s. Meanwhile, the elastic collision rate coefficient is increased to the 10-8 cm3/s level. The large good-to-bad collision ratio has allowed us to carry out evaporative cooling of 23Na87Rb with an efficiency of 1.7(2), increasing the phase-space density by a factor of 10. With further improvements, this technique holds great promises for creating a Bose-Einstein condensate of ultracold polar molecules.