Figure 1: A schematic of the experiment.
From: Doublon dynamics and polar molecule production in an optical lattice
Starting with a mixture of K, Rb and doublons (the smaller blue ball, the larger red ball and the pair grouped with grey background, respectively) in a 3D lattice, we sweep the magnetic field from above the s-wave Feshbach resonance (at 
) to below the resonance to create Feshbach molecules. These molecules are then transferred to their ro-vibrational ground state via STIRAP (stimulated Raman adiabatic passage). After unpaired atoms are removed with resonant light, the STIRAP process is reversed to transfer the ground-state molecules back to Feshbach molecules. The field is then swept above 
to dissociate the molecules and create doublons. After holding for a time, 
, at Bhold, we measure the conversion efficiency when sweeping the field below 
to re-form Feshbach molecules. To detect molecules, we use a rf pulse to spin flip the unpaired K atoms to a dark state (ball with black dashed edge) before dissociating the Feshbach molecules and imaging K atoms. The bottom panel illustrates possible dynamics of the doublons during Bhold. As shown schematically, lattice sites populated with a K and a Rb atom have an interaction energy shift 
. The K tunnelling energies in the lowest and first excited bands are denoted by 
and 
, respectively. Rb tunnelling happens at a slower rate since it experiences a deeper lattice.
