Abstract
Complex molecular structure demands customized solutions to laser cooling by extending its general set of principles and practices. Compared with other laser-cooled molecules, yttrium monoxide (YO) exhibits a large electron-nucleus interaction, resulting in a dominant hyperfine interaction over the electron spin-rotation coupling. The YO ground state is thus comprised of two manifolds of closely spaced states, with one of them possessing a negligible Landé g factor. This unique energy level structure favors dual-frequency dc magneto-optical trapping (MOT) and gray molasses cooling (GMC). We report exceptionally robust cooling of YO at 4 μK over a wide range of laser intensity, detunings (one- and two-photon), and magnetic field. The magnetic insensitivity enables the spatial compression of the molecular cloud by alternating GMC and MOT under the continuous operation of the quadrupole magnetic field. A combination of these techniques produces a laser-cooled molecular sample with the highest phase space density in free space.
Highlights
The techniques we develop to address the specific challenges and opportunities for yttrium monoxide (YO) can be applied to a class of molecules that share a similar energy level structure
We have investigated a wide range of cooling and trapping strategies based on the particular energy level structure of YO molecules, demonstrating both red-detuned and dual-frequency dc magneto-optical trapping (MOT) along with robust, fieldinsensitive sub-Doppler cooling to 4 μK with gray molasses cooling
We explored the relation of Raman resonance and gray molasses cooling (GMC), clarified the role of a Λ-type system in GMC, and demonstrated magnetically induced Sisyphus cooling
Summary
Ultracold molecules [1,2] offer a new platform for quantum chemistry [3,4,5], strongly correlated quantum systems [6], quantum information processing [7,8,9,10,11,12,13], and precision tests of fundamental physics [14,15,16,17,18,19,20,21,22]. To remove the large number of dark states in the form of rovibrational levels so that sufficient photon scatterings are ensured, cooling transitions should have maximally diagonal Franck-Condon factors [49] and optimized angular momentum selection rules [50] Following these initial proposals, the past few years have witnessed a rapid progress of laser cooling and trapping of molecules. Magnetically induced Sisyphus cooling [58,59,82,83,84] is observed under this field This robust cooling mechanism against large B allows us to demonstrate a novel scheme to significantly compress the molecular cloud by combining dc MOT trapping and sub-Doppler cooling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
