Magneto-Optical Trapping and Sub-Doppler Cooling of a Polyatomic Molecule

We report magneto-optical trapping (MOT) of a polyatomic molecule, calcium monohydroxide (CaOH). The MOT contains \(2.0(5)\times 10^4\) CaOH molecules at a peak density of \(3.0(8)\times10^{6}\) cm\(^{-3}\). CaOH molecules are further sub-Doppler laser cooled in an optical molasses, to a temperature of 110(4) \(\mu\)K. The temperatures and densities achieved here make CaOH a viable candidate for a wide variety of quantum science applications, including the creation of optical tweezer arrays of CaOH molecules. This work also suggests that laser cooling and magneto-optical trapping of many other polyatomic species will be both feasible and practical.