Transport Properties in a Mott-like State of Molecules

Ultracold gases in optical lattices are of great interest, because these systems bear a great potential for applications in quantum simulations and quantum information processing, in particular when using particles with a long-range dipole-dipole interaction, such as polar molecules. In an previous paper, the authors showed the preparation of a Mott-like state of molecules. The molecules are produced from an atomic Mott insulator with a density profile chosen such that the central region of the gas contains two atoms per lattice site. A Feshbach resonance is used to associate the atom pairs to molecules. Remaining atoms can be removed with laser light. In this paper, the transport properties in the Mott-like state is studied. A molecule can tunnel with an amplitude J_m to an adjacent site. If there is already another molecule at that site the molecules can collide inelastically, leading to loss of both molecules from the sample. This loss occurs with a rate coefficient Gamma which is typically much faster than J_m/planck. The fast on-site loss leads to a suppression of tunneling. Loss from the initial state effectively occurs with a rate Gamma_eff prop J_m ²/Gamma . This effect is studied experimentally at different lattice depths and the results are compared with theoretical predictions.