Towards magnetoassociation of the ultracold open-shell RbSr molecule

Ultracold dipolar molecules offer an ideal platform for investigations in the fields of quantum simulation, precision measurement and quantum chemistry. The range of possibilities offered by ultracold molecules could be substantially extended by employing the previously unexplored class of open-shell molecules like RbSr. Thanks to its unpaired valence electron RbSr possesses both a magnetic and an electric dipole moment offering an additional level of control with new exciting possibilities for quantum simulations.

Here we present our novel quantum-engineering approach towards the production of ultracold open-shell RbSr molecules that utilizes an ultra-narrow magnetic Feshbach resonance at 1311 G. Due to its extremely low relative width on the order of 10^-6, this is a serious experimental challenge.

Our state-of-the-art dual stabilization approach to the control of magnetic fields now enables us to achieve a relative magnetic field stability at the ppm level at fields beyond 1000 G. As a real-life benchmark of the capabilities of our system, we efficiently produce Rb Feshbach molecules on an ultranarrow 1.3-mG-wide resonance at 911.7 G. This is the first time that Feshbach molecule association is successful for such a narrow relative width and it is a crucial step towards the ultimate goal of magnetoassociating RbSr molecules.