Laser-Coolable Molecules Built from Coinage Metal and Carbon-Group Atoms

The broad scientific opportunities promised by ultracold molecules have spurred recent efforts to apply direct laser cooling to diverse sets of molecules. In recent years, increasing attention has been attracted by molecules that offer new resources to the areas of quantum science and precision measurements. This includes molecules with complex structure (often polyatomic molecules), where long-lived states arising from internal angular momenta are suspected to provide rich qubit platforms and/or internal co-magnetometers that provide robust systematic error rejection. Due to the difficulty associated with laser cooling polyatomic molecules, it is of interest to identify diatomic molecules that share these properties.

In this talk, after reviewing the recent progress achieved with complex structure in polyatomic molecules, we will focus on a new class of diatomic molecules that we have identified as potentially laser coolable: coinage metals bonded to carbon-group atoms. We will describe theoretical and experimental efforts focused on molecules such as CuX, AgX, and AuX (X=C and Pb). We will present theoretical results* predicting that these molecules combine many of the properties desirable for next-generation experiments using ultracold molecules. These include large relativistic enhancements, long-lived and highly polarizable X²Π_1/2 ground states with negligible magnetic-field sensitivity, and diagonal Franck-Condon factors that may enable optical cycling and laser cooling. We will also describe ongoing progress at Williams College to produce these molecules and study their optical spectra.

* Conducted in collaboration with Lan Cheng and the Johns Hopkins University