Loss suppression and interaction tuning in ultracold NaCs via double microwave shielding*

Strong suppression of two- and three-body losses via double microwave shielding allows us to evaporatively cool sodium-cesium molecules. This led to our recent realization of a BEC of dipolar NaCs molecules [1]. Microwave shielding with a single circularly polarized field has been shown to realize a strong collisional barrier, but can open a channel for three-body loss. By introducing a second microwave field, three-body loss is suppressed. With double microwave shielding we create BECs with a condensate fraction above 50% and a temperature of 6(2) nK. The degenerate molecular clouds are found to be stable, with a lifetime close to 2 seconds. More recently, we have explored methods for controlling s-wave contact and dipole-dipole interactions in the BEC.

[1] “Observation of Bose-Einstein condensation in a gas of dipolar molecules,” Bigagli, N., Yuan, W., Zhang, S., Bulatovic, B., Karman, T., Stevenson, I., Will, S., arXiv:2312.10965 (2023).