arXiv:1612.07196 · Physical Review A

Observation of interspecies Feshbach resonances in an ultracold K39−Cs133 mixture and refinement of interaction potentials

Michael Gröbner, Philipp Weinmann, Emil Kirilov, Hanns‐Christoph Nägerl, Paul S. Julienne, C. Ruth Le Sueur, Jeremy M. Hutson

Published Feb 28, 2017• 36 citations

arXiv HTML PDF

Abstract

We observe interspecies Feshbach resonances due to $s$-wave bound states in ultracold $^{39}\mathrm{K}\ensuremath{-}^{133}\mathrm{Cs}$ scattering for three different spin mixtures. The resonances are observed as joint atom loss and heating of the K sample. We perform least-squares fits to obtain improved K-Cs interaction potentials that reproduce the observed resonances, and carry out coupled-channel calculations to characterize the scattering and bound-state properties for $^{39}\mathrm{K}$-Cs, $^{40}\mathrm{K}$-Cs, and $^{41}\mathrm{K}$-Cs. Our results open up the possibilities of tuning interactions in K-Cs atomic mixtures and of producing ultracold KCs molecules.

DOI: 10.1103/physreva.95.022715

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arXiv:1612.07196 · Physical Review A

Observation of interspecies Feshbach resonances in an ultracold K39−Cs133 mixture and refinement of interaction potentials

Michael Gröbner, Philipp Weinmann, Emil Kirilov, Hanns‐Christoph Nägerl, Paul S. Julienne, C. Ruth Le Sueur, Jeremy M. Hutson

Published Feb 28, 2017• 36 citations

arXiv HTML PDF

Abstract

We observe interspecies Feshbach resonances due to

s

-wave bound states in ultracold

^{39}\mathrm{K}\ensuremath{-}^{133}\mathrm{Cs}

scattering for three different spin mixtures. The resonances are observed as joint atom loss and heating of the K sample. We perform least-squares fits to obtain improved K-Cs interaction potentials that reproduce the observed resonances, and carry out coupled-channel calculations to characterize the scattering and bound-state properties for

^{39}\mathrm{K}

-Cs,

^{40}\mathrm{K}

-Cs, and

^{41}\mathrm{K}

-Cs. Our results open up the possibilities of tuning interactions in K-Cs atomic mixtures and of producing ultracold KCs molecules.

DOI: 10.1103/physreva.95.022715

Related papers

Feshbach resonances, molecular bound states, and prospects of ultracold-molecule formation in mixtures of ultracold K and Cs

Hannah J. Patel, Caroline L. Blackley, Simon L. Cornish +1 more

We consider the possibilities for producing ultracold mixtures of K and Cs and forming KCs molecules by magnetoassociation. We carry out coupled-channel calculations of the interspecies scattering length for $^{39}\mathrm{KCs}$ , $^{41}\mathrm{KCs}$ , and $^{40}\mathrm{KCs}$ and characterize Feshbach resonances due to $s$ -wave and $d$ -wave bound states, with widths ranging from below 1 nG to 5 G. We also calculate the corresponding bound-state energies as a function of magnetic field. We give a general discussion of the combinations of intraspecies and interspecies scattering lengths needed to form low-temperature atomic mixtures and condensates and identify promising strategies for cooling and molecule formation for all three isotopic combinations of K and Cs.We consider the possibilities for producing ultracold mixtures of K and Cs and forming KCs molecules by magnetoassociation. We carry out coupled-channel calculations of the interspecies scattering length for $^{39}\mathrm{KCs}$, $^{41}\mathrm{KCs}$, and $^{40}\mathrm{KCs}$ and characterize Feshbach resonances due to $s$-wave and $d$-wave bound states, with widths ranging from below 1 nG to 5 G. We also calculate the corresponding bound-state energies as a function of magnetic field. We give a general discussion of the combinations of intraspecies and interspecies scattering lengths needed to form low-temperature atomic mixtures and condensates and identify promising strategies for cooling and molecule formation for all three isotopic combinations of K and Cs.

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We observe interspecies Feshbach resonances due to

s

-wave bound states in ultracold

^{39}\mathrm{K}\ensuremath{-}^{133}\mathrm{Cs}

^{39}\mathrm{K}

-Cs,

^{40}\mathrm{K}

-Cs, and

^{41}\mathrm{K}

-Cs. Our results open up the possibilities of tuning interactions in K-Cs atomic mixtures and of producing ultracold KCs molecules.

^{39}\mathrm{KCs}

^{41}\mathrm{KCs}

, and

^{40}\mathrm{KCs}

and characterize Feshbach resonances due to

s

-wave and

d

-wave bound states, with widths ranging from below 1 nG to 5 G. We also calculate the corresponding bound-state energies as a function of magnetic field. We give a general discussion of the combinations of intraspecies and interspecies scattering lengths needed to form low-temperature atomic mixtures and condensates and identify promising strategies for cooling and molecule formation for all three isotopic combinations of K and Cs.

s

-wave channels and the rest to

p

-wave channels. We use the

s

-wave resonances to refine the ground-state potentials of LiCs in the coupled-channel calculations and then obtain an accurate characterization of the scattering and bound-state properties of the mixtures. Our results will be useful for future experiments with ultracold $^{7}\mathrm{Li}{\text{\ensuremath{-}}}^{133}\mathrm{Cs}$ mixtures.

We report on the observation of 19 interspecies Feshbach resonances in an optically trapped ultracold Bose-Fermi mixture of

{}^{133}\text{Cs}

and

{}^{6}\text{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.

We have studied interspecies scattering in an ultracold mixture of

{}^{87}

Rb and

{}^{133}

Cs atoms, both in their lowest-energy 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 $\text{MHz}\ifmmode\times\else\texttimes\fi{}h$. 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 successfully prepared an optically trapped ultracold mixture of

{}^{23}

Na and

{}^{87}

Rb atoms and studied their interspecies Feshbach resonances. Using two different spin combinations, several

s

- and

p

-wave resonances are identified by observing high inelastic losses and temperature increases for both species near resonant magnetic field values. The two

s

-wave resonances observed below 500 G between atoms in their lowest-energy levels are possible candidates for Feshbach molecule association. Our results are well characterized by a coupled-channel model which also refines the ground-state interaction potentials between

{}^{23}

Na and

{}^{87}

Rb. This work opens up the prospect for preparing ultracold ensembles of ground-state bosonic NaRb molecules which are chemically stable and can provide strong dipolar interactions.