Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We have studied interspecies scattering in an ultracold mixture of 87 Rb and 133 Cs atoms, both in their lowestenergy spin states. The three-body loss signatures of 30 incoming s-and p-wave magnetic Feshbach resonances over the range 0 to 667 G have been cataloged. Magnetic field modulation spectroscopy was used to observe molecular states bound by up to 2.5 MHz × h. We have created RbCs Feshbach molecules using two of the resonances. Magnetic moment spectroscopy along the magnetoassociation pathway from 197 to 182 G gives results consistent with the observed and calculated dependence of the binding energy on magnetic field strength. We have set up a coupled-channel model of the interaction and have used direct least-squares fitting to refine its parameters to fit the experimental results from the Feshbach molecules, in addition to the Feshbach resonance positions and the spectroscopic results for deeply bound levels. The final model gives a good description of all the experimental results and predicts a large resonance near 790 G, which may be useful for tuning the interspecies scattering properties. Quantum numbers and vibrational wave functions from the model can also be used to choose optimal initial states of Feshbach molecules for their transfer to the rovibronic ground state using stimulated Raman adiabatic passage.

We have performed high-resolution two-photon dark-state spectroscopy of an ultracold gas of 87 Rb2 molecules in the a 3 Σ + u state at a magnetic field of about 1000 G. The vibrational ladder as well as the hyperfine and low-lying rotational structure is mapped out. Energy shifts in the spectrum are observed due to singlet-triplet mixing at binding energies as deep as a few hundred GHz×h. This information together with data from other sources is used to optimize the potentials of the a 3 Σ + u and X 1 Σ + g states in a coupled-channel model. We find that the hyperfine structure depends weakly on the vibrational level. This provides a possible explanation for inaccuracies in recent Feshbach resonance calculations.

We show that, by loading a Bose-Einstein condensate of two different atomic species into an optical lattice, it is possible to achieve a Mott-insulator phase with exactly one atom of each species per lattice site. A subsequent photoassociation leads to the formation of one heteronuclear molecule with a large electric dipole moment, at each lattice site. The melting of such a dipolar Mott insulator creates a dipolar superfluid, and eventually a dipolar molecular condensate.

We report on the observation of nineteen interspecies Feshbach resonances in an optically trapped ultracold Bose-Fermi mixture of 133 Cs and 6 Li in the two energetically lowest spin states. We assign the resonances to s-and p-wave molecular channels by a coupled-channels calculation, resulting in an accurate determination of LiCs ground state potentials. Fits of the resonance position based on the undressed Asymptotic Bound State model do not provide the same level of accuracy as the coupled-channels calculation. Several broad s-wave resonances provide prospects to create fermionic LiCs molecules with a large dipole moment via Feshbach association followed by stimulated Raman passage. Two of the s-wave resonances overlap with a zero crossing of the Cs scattering length which offers prospects for the investigation of polarons in an ultracold Li-Cs mixture. [4][5][6], which gives access to the study of many-body physics, quantum chemistry and precision measurements [7,8]. With a permanent electric dipole moment of 5.5 Debye [9,10], the largest among all alkali-metal dimers, a system of LiCs molecules in their energetically lowest states [11] is considered to be an excellent candidate for the investigation of dipolar quantum gases [12]. Another application of the precise tunability close to a FR is the study of Efimov trimers [13]. The large mass ratio of m Cs /m Li = 22 results in an advantageous universal scaling factor of 4.88 instead of 22.7 as found for a system of equal masses [14], resulting in excellent conditions for observing a series of several Efimov resonances, which, so far, has not been achieved. Interspecies FR can be also used to control the interaction between an impurity and a Bose-Einstein Condensate (BEC). Such a system can directly be mapped to the Fröhlich polaron Hamiltonian [15][16][17], which describes the interaction of an electron gas with the charged lattice atoms in a crystal. As the excitations in a Bose-Einstein condensate represent the lattice phonons, a FR allows the precise adjustment of the modeled phonon-electron coupling strength α, thus allowing one to explore fundamental solid-state systems.FRs between different alkaline species have been identified for a variety of Bose-Bose [18][19][20][21] Cs were studied by means of thermalization measurements at zero magnetic field [40], however, the tunability of the interspecies scattering properties via tuning the magnetic field has yet remained unexplored. Here, we report on the observation of nineteen interspecies loss features in different spin channels of an optically trapped 6 Li -133 Cs mixture, by scanning a homogeneous magnetic field (Feshbach spectroscopy). The magnetic field positions and widths of the observed FRs are analyzed in a full coupled-channels calculation, allowing a consistent assignment of the resonances.We have realized an all-optical preparation scheme to simultaneously trap an ultracold 6 Li -133 Cs mixture with a magnetic field control up to 1300 G by sequentially transferring Li and Cs atoms into an optic...

We have studied magnetic Feshbach resonances in an ultracold sample of Na prepared in the absolute hyperfine ground state. We report on the observation of three s-, eight d-, and three g-wave Feshbach resonances, including a more precise determination of two known s-wave resonances, and one s-wave resonance at a magnetic field exceeding 200 mT. Using a coupled-channels calculation we have improved the sodium ground-state potentials by taking into account these new experimental data and derived values for the scattering lengths. In addition, a description of the molecular states leading to the Feshbach resonances in terms of the asymptotic-bound-state model is presented.