Realizing the full potential of ultracold polar molecules requires cooling interacting molecular gases deeply into the quantum-degenerate regime. This paper demonstrates evaporative cooling of a three-dimensional gas of fermionic sodium-potassium molecules to well below the Fermi temperature using microwave shielding. The microwave dressing induces strong tunable dipolar interactions, leading to high elastic collision rates that exceed inelastic ones. This allows cooling to 21 nanokelvin (0.36 times the Fermi temperature), opening paths to exploring many-body phenomena with strong dipolar interactions.

Andreas Schindewolf, Roman Bause, Xing-Yan Chen, Marcel Duda, Tijs Karman, Immanuel Bloch, Xin-Yu Luo