Dipolar evaporation and resonant shielding of KRb molecules in quasi-2D

Quantum degenerate gases of polar molecules open new possibilities for engineering strongly-correlated quantum matter. However, tuning molecular interactions to create a system that is both long-lived and strongly dipolar has remained an outstanding experimental challenge. We have implemented two strategies for controlling interactions in a quasi-2D geometry [1-2]. First, by polarizing the molecular dipoles perpendicular to the 2D plane, we induce repulsive dipolar interactions, which provide elastic collisions while suppressing losses. We achieve a ratio of elastic to inelastic collision rates of ~200, and demonstrate direct evaporation to below the Fermi temperature. Second, we observe resonant shielding of losses, which arises from dipolar coupling between two pairs of rotational states made degenerate by the external electric field. At the optimal shielding, we suppress the loss rate by an order of magnitude below the background value. These results provide a starting point for future explorations of collective dipolar phenomena in 2D.

[1] G. Valtolina, K. Matsuda, W. G. Tobias, J.-R. Li, L. De Marco, and J. Ye, Nature 588, 239-243 (2020).

[2] K. Matsuda, L. De Marco, J.-R. Li, W. G. Tobias, G. Valtolina, G. Quéméner, and J. Ye, Science 370, 1324-1327 (2020).