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Observation of Bose–Einstein condensation of dipolar molecules

Abstract

Ensembles of particles governed by quantum mechanical laws exhibit intriguing emergent behaviour. Atomic quantum gases1,2, liquid helium3,4 and electrons in quantum materials5,6,7 all exhibit distinct properties because of their composition and interactions. Quantum degenerate samples of ultracold dipolar molecules promise the realization of new phases of matter and new avenues for quantum simulation8 and quantum computation9. However, rapid losses10, even when reduced through collisional shielding techniques11,12,13, have so far prevented evaporative cooling to a Bose–Einstein condensate (BEC). Here we report on the realization of a BEC of dipolar molecules. By strongly suppressing two- and three-body losses via enhanced collisional shielding, we evaporatively cool sodium–caesium molecules to quantum degeneracy and cross the phase transition to a BEC. The BEC reveals itself by a bimodal distribution when the phase-space density exceeds 1. BECs with a condensate fraction of 60(10)% and a temperature of 6(2) nK are created and found to be stable with a lifetime close to 2 s. This work opens the door to the exploration of dipolar quantum matter in regimes that have been inaccessible so far, promising the creation of exotic dipolar droplets14, self-organized crystal phases15 and dipolar spin liquids in optical lattices16.

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Fig. 1: BEC of dipolar NaCs molecules enabled by microwave shielding.
Fig. 2: Formation of the molecular BEC.
Fig. 3: Evaporative cooling of NaCs molecules to quantum degeneracy.
Fig. 4: Time-of-flight expansion.
Fig. 5: BEC lifetime.

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Data availability

The experimental data that support the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.

Code availability

All relevant codes are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank C. Greene, A. Elkamshishy and S. Singh for their discussions and preliminary calculations on the field-linked bound states in the shielding potentials, and R. Wooten, T. Yefsah and M. Zwierlein for critical reading and helpful comments on the paper. We are grateful to A. Lam and C. Warner for their contributions to the construction of the experimental apparatus. We also thank I. Bloch, T.-L. Ho and V. Vuletić for their discussions. We acknowledge E. Bellingham and H. Kwak for their experimental assistance. We thank Rohde & Schwarz for the loan of equipment. This work was supported by an NSF CAREER Award (award no. 1848466), an ONR DURIP Award (award no. N00014-21-1-2721), a grant from the Gordon and Betty Moore Foundation (award no. GBMF12340) and a Lenfest Junior Faculty Development Grant from Columbia University. W.Y. acknowledges support from the Croucher Foundation. I.S. was supported by the Ernest Kempton Adams Fund. S.W. acknowledges additional support from the Alfred P. Sloan Foundation.

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All authors contributed substantially to the work presented in this paper. N.B., W.Y., S.Z. and I.S. carried out the experiments and improved the experimental setup. T.K. performed the theoretical calculations. S.W. supervised the study. N.B., I.S. and S.W. wrote the paper. All authors contributed to the development of the experimental concepts, interpretation of the data and reviewed the paper.

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Correspondence to Sebastian Will.

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Nature thanks Lauriane Chomaz, Simon Cornish and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data figures and tables

Extended Data Fig. 1 Microwave setup.

a, Block diagram of the microwave components producing the σ+ field. b, Block diagram of the microwave components producing the π field. MHz-level detunings are omitted from the shown frequencies of the source.

Extended Data Fig. 2 Comparison of fitting models.

Ratio of χ2-values for Gaussian and bimodal fits. The vertical dashed line marks the onset of the phase transition.

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Bigagli, N., Yuan, W., Zhang, S. et al. Observation of Bose–Einstein condensation of dipolar molecules. Nature (2024). https://doi.org/10.1038/s41586-024-07492-z

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