Feshbach molecules from an atomic Mott insulator

Feshbach molecules from bosonic atomic species have proven to be very unstable with respect to inelastic collisions [1]. As a result, the typical lifetime observed for a cloud of ultracold $^{87}$Rb$_2$ molecules stored in an optical dipole trap is limited to a few ms.\\ Here, we report on the observation of long-lived Feshbach molecules in an optical lattice. A BEC of $^{87}$Rb atoms is loaded into the lowest Bloch band of a 3D optical lattice operated at a wavelength of $830~$nm. By ramping up the lattice depth, the atomic gas enters the Mott insulator regime. A magnetic-field ramp through the Feshbach resonance at $1007~$G creates molecules [2]. Lattice sites initially occupied with more than 2 atoms experience fast inelastic collisional losses. The observed lifetime of the remaining molecules is $\sim 100~$ms, which is much longer than for a pure molecular sample in an optical dipole trap. Similar results have recently been reported in Ref.[3]. The increased lifetime is an important step on the route to a BEC of molecules in the vibrational ground state [4].\\ \\ $[1]$ T. Mukaiyama et al., Phys. Rev. Lett. 92, 180402 (2004) \\ $[2]$ S. D\"urr et al., Phys. Rev. Lett. 92, 020406 (2004) \\ $[3]$ G. Thalhammer et al., cond-mat/0510755 \\ $[4]$ D. Jaksch et al., Phys. Rev. Lett. 89, 040402 (2002)\\