Towards fermionic open-shell RbSr molecules

Ultracold dipolar molecules are a promising platform for quantum simulation, precision measurement and quantum chemistry. Ultracold molecules produced so far are closed-shell molecules, which limits their range of applications. Our goal is to produce ultracold fermionic RbSr molecules, which are dipolar open-shell molecules, in order to extend the range of possibilities.

Here, we present a novel approach to create these molecules, and our progress towards this goal. Our approach uses confinement induced resonances (CIR) in a strongly interacting Bose-Fermi mixture and overcomes the challenge that magnetic Feshbach resonances which are typically used to create ultracold molecules are extremely narrow between alkali and alkaline-earth atoms. CIRs resonantly couple two atoms jointly confined in a tight trap to a very weakly bound molecular state, in an excited state of the center-of-mass motion in the trap. Our experiment will start by preparing a strongly interacting ⁸⁷Rb-⁸⁷Sr Bose-Fermi mixture. In order to suppress inelastic collisions, we intend to first prepare an n=1 Mott insulator of Rb in an optical lattice and then overlap it with a spin-polarized Fermi gas of Sr. After molecule creation by adiabatically ramping the lattice depth across a CIR, we plan to perform STIRAP to the molecular ground state.