Microwave Shielding of Bosonic Ground State Molecules

We report on the collisional stabilization of ultracold sodium-cesium (NaCs) molecules via microwave shielding. Through the use of a blue-detuned, circularly polarized microwave field, we prepare NaCs molecules in a dressed state that suppresses collisional losses by over two orders of magnitude.

For samples of 3 × 10⁴ molecules with a peak density of 1 × 10¹² cm^-3, we enhance the lifetime to beyond 1 s. We study the elastic collisional properties of the dressed gas using cross-dimensional thermalization. We observe an enhancement of elastic collision rates as a result of dipolar interactions. At the same time, the rates of cross-dimensional thermalization are slower than initially expected, which we attribute to the anisotropic character of dipolar interactions. Finally, we demonstrate evaporative cooling of our gas, increasing its phase-space density by a factor of 20.

With these advances, bosonic NaCs molecules are becoming a promising platform for quantum many-body physics, quantum simulation, and quantum computing.