Rb-Cs: Dipolar quantum matter with ultracold molecules

Institut für Experimentalphysik,
University of Innsbruck, and
Austrian Academy of Sciences,
Innsbruck, Austria


The Team

Photos IQOQI/Knabl

Former Team Members

  • Lukas Reichsöllner, 2010-2017, PhD thesis
  • Silva Mezinska, 2014-2017
  • Beatrix Mayr, 2015-2016
  • Tetsu Takekoshi, 2010-2015, (now in the group of Prof. Rainer Blatt)
  • Francesca Ferlaino, 2009-2014, (now professor at the University of Innsbruck and research director at the IQOQI)
  • Michael Kugler, 2012-2013
  • Verena Pramhaas, 2012-2013
  • Carl Hippler, 2012-2013, diploma thesis

Scientific Output


Recognition award of the jury of the best student paper award

Lukas Reichsöllner (third from right) and Andreas Schindewolf (second from right) received the recognition award of the jury of the of the best student paper award "Anerkennungspreis der Jury zum Best Student Paper Award 2017" for developing a novel method to produce low-entropy samples of ultracold heteronuclear molecules, Phys. Rev. Lett. 118, 073201 (2017). The recognition award from the university was handed out by Vice Rector for Research Univ.-Prof. Dr. Ulrike Tanzer (far right). In the review process the international significance of the new method, with regard to the future development of the field of ultracold dipolar molecules, was attested.
We congratulate also the other recipients, especially our colleagues from the theory department Stefan Ostermann (second from left), who was also awarded a recognition award, and Michael Schuler, who received the main award.

Photo Uni Innsbruck.


Quantum engineering of a low-entropy gas of heteronuclear bosonic molecules in an optical lattice

L. Reichsöllner*, A. Schindewolf*, T. Takekoshi, R. Grimm, and H.-C. Nägerl

*These authors contributed equally to this work.

We demonstrate a generally applicable technique for mixing two-species quantum degenerate bosonic samples in the presence of an optical lattice, and we employ it to produce low-entropy samples of ultracold 87Rb133Cs Feshbach molecules with a lattice filling fraction exceeding 30%. Starting from two spatially separated Bose-Einstein condensates of Rb and Cs atoms, Rb-Cs atom pairs are efficiently produced by using the superfluid-to-Mott insulator quantum phase transition twice, first for the Cs sample, then for the Rb sample, after nulling the Rb-Cs interaction at a Feshbach resonance's zero crossing. We form molecules out of atom pairs and characterize the mixing process in terms of sample overlap and mixing speed. The dense and ultracold sample of more than 5000 RbCs molecules is an ideal starting point for experiments in the context of quantum many-body physics with long-range dipolar interactions.

Phys. Rev. Lett. 118, 073201 (2017), arXiv:1607.06536



Recognition award of the jury of the science prize of Innsbruck

The RbCs team received the recognition award of the jury of the science prize of Innsbruck "Anerkennungspreis der Jury des Preises der Landeshauptstadt Innsbruck". The recognition award was awarded for the publication "Ultracold dense samples of dipolar RbCs molecules in the rovibrational and hyperfine ground state", T. Takekoshi et al., Phys. Rev. Lett. 113, 205301 (2014). In the evaluation process the publication scored 398 of 400 possible points and was attested to be of international significance. The photo of the award ceremony shows Vice Rector for Research Univ.-Prof. Dr. Sabine Schindler (far left) with the PhD students Andreas Schindewolf (second from left) and Lukas Reichsöllner (third from left) from the RbCs team.

Photo Uni Innsbruck.


Ultracold dense samples of dipolar RbCs molecules in the rovibrational and hyperfine ground state

T. Takekoshi, L. Reichsöllner, A. Schindewolf, J. M. Hutson, C. R. Le Sueur, O. Dulieu, F. Ferlaino, R. Grimm, H.-C. Nägerl

We produce ultracold dense trapped samples of 87Rb133Cs molecules in their rovibrational ground state, with full nuclear hyperfine state control, by stimulated Raman adiabatic passage (STIRAP) with efficiencies of 90%. We observe the onset of hyperfine-changing collisions when the magnetic field is ramped so that the molecules are no longer in the hyperfine ground state. A strong quadratic shift of the transition frequencies as a function of applied electric field shows the strongly dipolar character of the RbCs ground-state molecule. Our results open up the prospect of realizing stable bosonic dipolar quantum gases with ultracold molecules.

Phys. Rev. Lett. 113, 205301 (2014) , arXiv:1405.6037



Towards the production of ultracold ground-state RbCs molecules: Feshbach resonances, weakly bound states, and coupled-channel model

T. Takekoshi, M. Debatin, R. Rameshan, F. Ferlaino, R. Grimm, H.-C. Nägerl, C.R. Le Sueur, J.M. Hutson, P.S. Julienne, S. Kotochigova, E. Tiemann

We have studied interspecies scattering in an ultracold mixture of 87Rb and 133Cs 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 catalogued. Magnetic field modulation spectroscopy was used to observe molecular states bound by up to 2.5 MHz x h. Magnetic moment spectroscopy along the magneto-association 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 created RbCs Feshbach molecules using two of the resonances. 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 wavefunctions 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 (STIRAP).

Phys. Rev. A 85, 032506 (2012), arxiv:1201.1438v2



Molecular spectroscopy for ground-state transfer of ultracold RbCs molecules

M. Debatin, T. Takekoshi, R. Rameshan, L. Reichsöllner, F. Ferlaino, R. Grimm, R. Vexiau, N. Bouloufa, O. Dulieu, H.-C. Nägerl

We perform one- and two-photon high resolution spectroscopy on ultracold samples of RbCs Feshbach molecules with the aim to identify a suitable route for efficient ground-state transfer in the quantum-gas regime to produce quantum gases of dipolar RbCs ground-state molecules. One-photon loss spectroscopy allows us to probe deeply bound rovibrational levels of the mixed excited (A1Σ+ - b3Π0)0+ molecular states. Two-photon dark state spectroscopy connects the initial Feshbach state to the rovibronic ground state. We determine the binding energy of the lowest rovibrational level |v"=0,J"=0> of the X1Σ+ ground state to be DX0 = 3811.5755(16) 1/cm, a 300-fold improvement in accuracy with respect to previous data. We are now in the position to perform stimulated two-photon Raman transfer to the rovibronic ground state.

Phys. Chem. Chem. Phys. 13, 18926 (2011), arXiv:1106.0129



Production of a dual-species Bose-Einstein condensate of Rb and Cs atoms

A. D. Lercher, T. Takekoshi, M. Debatin, B. Schuster, R. Rameshan, F. Ferlaino, R. Grimm, H.-C. Nägerl

We report the simultaneous production of Bose-Einstein condensates (BECs) of 87Rb and 133Cs atoms in separate optical traps. The two samples are mixed during laser cooling and loading but are separated by 400 μm for the final stage of evaporative cooling. This is done to avoid considerable interspecies three-body recombination, which causes heating and evaporative loss. We characterize the BEC production process, discuss limitations, and outline the use of the dual-species BEC in future experiments to produce rovibronic ground state molecules, including a scheme facilitated by the superfluid-to-Mott-insulator (SF-MI) phase transition.

Eur. Phys. J. D 65, 3 (2011), arxiv:1101.1409



Observation of interspecies Feshbach resonances in an ultracold Rb-Cs mixture

K. Pilch, A. D. Lange, A. Prantner, G. Kerner, F. Ferlaino, H.-C. Nägerl, R. Grimm

We report on the observation of interspecies Feshbach resonances in an ultracold, optically trapped mixture of Rb and Cs atoms. In a magnetic field range up to 300 G we find 23 interspecies Feshbach resonances in the lowest spin channel and 2 resonances in a higher channel of the mixture. The extraordinarily rich Feshbach spectrum suggests the importance of different partial waves in both the open and closed channels of the scattering problem along with higher-order coupling mechanisms. Our results provide, on one hand, fundamental experimental input to characterize the Rb-Cs scattering properties and, on the other hand, identify possible starting points for the association of ultracold heteronuclear RbCs molecules.

Phys. Rev. A 79, 042718 (2009), arXiv:0812.3287



Determination of atomic scattering lengths from measurements of molecular binding energies near Feshbach resonances

A. D. Lange, K. Pilch, A. Prantner, F. Ferlaino, B. Engeser, H.-C. Nägerl, R. Grimm, and C. Chin

We present an analytic model to calculate the atomic scattering length near a Feshbach resonance from data on the molecular binding energy. Our approach considers finite-range square-well potentials and can be applied near broad, narrow, or even overlapping Feshbach resonances. We test our model on Cs2 Feshbach molecules. We measure the binding energy using magnetic-field modulation spectroscopy in a range where one broad and two narrow Feshbach resonances overlap. From the data we accurately determine the Cs atomic scattering length and the positions and widths of two particular resonances.

Phys. Rev. A 79, 013622 (2009), arXiv:0810.5503



SFB F15: Control and Measurement of Coherent Quantum Systems
Project 16

EUROCORES program EuroQUAM: Cold Quantum Matter
Project QUDIPMOL: Quantum-degenerate dipolar gases of bialkali molecules

SFB F40: Foundations and Applications of Quantum Science
Project 06: Dipolar quantum gases

Forschergruppe FOR 2247: From few to many-body physics with dipolar quantum gases
Project E6 (FWF project I 2789): Quantum Dynamics of Strongly Correlated RbCs Dipolar Quantum Gases
DACH lead agency: DFG

Wittgensteinpreis Z 336: exp. quantum physics, quantum gases, low-dimensional quantum systems, ultracold molecules
last change: 22-01-2018 by AS