Herbert P. Broida Prize: Laser Cooling of Polyatomic Molecules

The tremendous scientific opportunities presented by ultracold molecules have driven rapid progress in both the assembly of diatomic molecules from ultracold atoms and the direct cooling of diatomic and polyatomic molecules. Diatomic species have been magneto-optically trapped and sub-Doppler cooled and their collisions have been studied in several experimental systems, including magnetic traps and merged optical tweezers. The pioneering work that led to advances in direct cooling began with Stark deceleration, buffer-gas cooling and loading of traps, buffer-gas beam sources, mechanical slowing, and a variety of electromagnetic trapping and cooling mechanisms. As the field of cold and ultracold molecules has grown, polyatomic molecules have attracted new focus as potential novel quantum resources that have distinct advantages (and challenges) compared to both atoms and diatomic molecules. For example, all polyatomic molecules have long-lived states arising from nuclear motion with angular momentum about the internuclear axis. These states exhibit linear, Debye-level Stark shifts at very low applied electric fields and offer distinct Stark-shifted level structures that are absent in laser-coolable diatomic molecules. These and other features in polyatomic molecules can be applied to quantum simulation and to searches for both dark matter and other particle physics beyond the Standard Model, potentially at the 1 PeV scale. Generic classes of polyatomic molecules have been identified as amenable to laser cooling into the ultracold (~1 μK) regime. One class is that of metal oxide radicals, which includes linear, symmetric top, and asymmetric top species. In this talk, I will discuss some of the past experiments that brought us to this point, and the challenges and scientific opportunities with the laser cooling of polyatomic molecules. Results on SrOH, YbOH, CaOH and CaOCH3 will be discussed, as well as preliminary work on more complex species.