Polyatomic molecules with multivalent optical cycling centers

Direct laser cooling and trapping of polyatomic molecules promise new opportunities in precision metrology, quantum information, many-body physics, and fundamental chemistry. Contemporary experimental and theoretical efforts have mostly focused on cycling photons via a single sσ electron localized to an alkaline earth-like metal center. Here, we report new pathways for laser cooling polyatomic molecules with multiple cycling electrons hosted by post-transition metal and metalloid centers (i.e. Al, Si, P). We have characterized the electronic structure and rovibrational branching of several prototypical candidates using ab initio quantum chemical methods, finding quasi-closed photon cycling schemes with highly diagonal, visible-wavelength transitions. In the process, we have identified new heuristics for engineering laser-coolable polyatomic molecules with higher metal valences. Our findings help elucidate the interplay between hybridization, repulsion, and ionicity in optically active species and provide a roadmap towards using laser-coolable molecules with complex electronic structure as a resource for quantum science and measurement.