Observation of interspecies6Li-133Cs Feshbach resonances

Abstract

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...

Feshbach resonances, weakly bound molecular states, and coupled-channel potentials for cesium at high magnetic fields

“…[18]. The present work is important not only for experiments on Cs, but also provides important information for ongoing and future experiments involving Cs mixtures, such as RbCs [85], LiCs [86,87], and other interesting combinations.…”

Long-range interactions between polar alkali-metal diatoms in external electric fields

“…The most spectacular experimental achievements on ultracold dipolar molecular gases have been performed on KRb molecules [8,9,11,19] which motivated a wealth of theoretical investigations on this species [17,[20][21][22][23]. An * maxence.lepers@u-psud.fr accurate description of long-range interactions involving the other heteronuclear alkali diatoms is strongly needed since they draw rising attention [24][25][26][27][28][29][30][31][32]. Considering two identical polar molecules at large distances R (in atomic units 1 a.u.…”

Ultralong-range Rydberg molecules in combined electric and magnetic fields

“…The external degrees of freedom can be accessed by designing and switching almost arbitrarily shaped traps [1][2][3] which are created by external electric, magnetic or electromagnetic fields. Furthermore, interatomic interaction strength can be tuned via magnetic or optical Feshbach resonances [4][5][6][7][8][9]. A prominent new species are the weakly bound ultralong-range diatomic molecules composed of a ground state and a Rydberg atom.…”