Molecules cooled below the Doppler limit

Abstract

Magneto-optical trapping and sub-Doppler cooling have been essential to most experiments with quantum degenerate gases, optical lattices, atomic fountains and many other applications. A broad set of new applications await ultracold molecules1, and the extension of laser cooling to molecules has begun2,3,4,5,6. A magneto-optical trap (MOT) has been demonstrated for a single molecular species, SrF7,8,9, but the sub-Doppler temperatures required for many applications have not yet been reached. Here we demonstrate a MOT of a second species, CaF, and we show how to cool these molecules to 50 μK, well below the Doppler limit, using a three-dimensional optical molasses. These ultracold molecules could be loaded into optical tweezers to trap arbitrary arrays10 for quantum simulation11, launched into a molecular fountain12,13 for testing fundamental physics14,15,16,17,18, and used to study collisions and chemistry19 between atoms and molecules at ultracold temperatures.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: Schematic of the experiment.
Figure 2: Characterization of the MOT.
Figure 3: Cooling the MOT by ramping down the intensity.
Figure 4: Sub-Doppler cooling.

References

  1. 1

    Carr, L. D., DeMille, D., Krems, R. V. & Ye, J. Cold and ultracold molecules: science, technology and applications. New J. Phys. 11, 055049 (2009).

  2. 2

    Shuman, E. S., Barry, J. F. & DeMille, D. Laser cooling of a diatomic molecule. Nature 467, 820–823 (2010).

  3. 3

    Hummon, M. T. et al. 2D magneto-optical trapping of diatomic molecules. Phys. Rev. Lett. 110, 143001 (2013).

  4. 4

    Zhelyazkova, V. et al. Laser cooling and slowing of CaF molecules. Phys. Rev. A 89, 053416 (2014).

  5. 5

    Hemmerling, B. et al. Laser slowing of CaF molecules to near the capture velocity of a molecular MOT. J. Phys. B 49, 174001 (2016).

  6. 6

    Kozyryev, I. et al. Sisyphus laser cooling of a polyatomic molecule. Phys. Rev. Lett. 118, 173201 (2017).

  7. 7

    Barry, J. F., McCarron, D. J., Norrgard, E. B., Steinecker, M. H. & DeMille, D. Magneto-optical trapping of a diatomic molecule. Nature 512, 286–289 (2014).

  8. 8

    McCarron, D. J., Norrgard, E. B., Steinecker, M. H. & DeMille, D. Improved magneto-optical trapping of a diatomic molecule. New J. Phys. 17, 035014 (2015).

  9. 9

    Norrgard, E. B., McCarron, D. J., Steinecker, M. H., Tarbutt, M. R. & DeMille, D. Submillikelvin dipolar molecules in a radio-frequency magneto-optical trap. Phys. Rev. Lett. 116, 063004 (2016).

  10. 10

    Barredo, D., de Léséleuc, S., Lienhard, V., Lahaye, T. & Browaeys, A. An atom-by-atom assembler of defect-free arbitrary 2d atomic arrays. Science 354, 1021–1023 (2016).

  11. 11

    Micheli, A., Brennen, G. K. & Zoller, P. A toolbox for lattice-spin models with polar molecules. Nat. Phys. 2, 341–347 (2006).

  12. 12

    Tarbutt, M. R., Sauer, B. E., Hudson, J. J. & Hinds, E. A. Design for a fountain of YbF molecules to measure the electron’s electric dipole moment. New J. Phys. 15, 053034 (2013).

  13. 13

    Cheng, C. et al. Molecular fountain. Phys. Rev. Lett. 117, 253201 (2016).

  14. 14

    Hudson, J. J. et al. Improved measurement of the shape of the electron. Nature 473, 493–496 (2011).

  15. 15

    Baron, J. et al. Order of magnitude smaller limit on the electric dipole moment of the electron. Science 343, 269–272 (2014).

  16. 16

    Kajita, M. Variance measurement of mp/me using cold molecules. Can. J. Phys. 87, 743–748 (2009).

  17. 17

    Hunter, L. R., Peck, S. K., Greenspon, A. S., Alam, S. S. & DeMille, D. Prospects for laser cooling TlF. Phys. Rev. A 85, 012511 (2012).

  18. 18

    Cahn, S. B. et al. Zeeman-tuned rotational-level crossing spectroscopy in a diatomic free radical. Phys. Rev. Lett. 112, 163002 (2014).

  19. 19

    Krems, R. V. Cold controlled chemistry. Phys. Chem. Chem. Phys. 10, 4079–4092 (2008).

  20. 20

    Steinecker, M. H., McCarron, D. J., Zhu, Y. & DeMille, D. Improved radio-frequency magneto-optical trap of SrF molecules. Chem. Phys. Chem. 17, 3664–3669 (2016).

  21. 21

    Tarbutt, M. R. & Steimle, T. C. Modeling magneto-optical trapping of CaF molecules. Phys. Rev. A 92, 053401 (2015).

  22. 22

    Devlin, J. A. & Tarbutt, M. R. Three-dimensional Doppler, polarization-gradient, and magneto-optical forces for atoms and molecules with dark states. New J. Phys. 18, 123017 (2016).

  23. 23

    Dalibard, J. & Cohen-Tannoudji, C. Laser cooling below the Doppler limit by polarization gradients: simple theoretical models. J. Opt. Soc. Am. B 6, 2023–2045 (1989).

  24. 24

    Ungar, P. J., Weiss, D. S., Riis, E. & Chu, S. Optical molasses and multilevel atoms: theory. J. Opt. Soc. Am. B 6, 2058–2071 (1989).

  25. 25

    Boiron, D., Triché, C., Meacher, D. R., Verkerk, P. & Grynberg, G. Three-dimensional cooling of cesium atoms in four-beam gray optical molasses. Phys. Rev. A 52, R3425–R3428 (1995).

  26. 26

    Fernandes, D. R. et al. Sub-Doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses. Europhys. Lett. 100, 63001 (2012).

  27. 27

    Prehn, A., Ibrügger, M., Glöckner, R., Rempe, G. & Zeppenfeld, M. Optoelectrical cooling of polar molecules to submillikelvin temperatures. Phys. Rev. Lett. 116, 063005 (2016).

  28. 28

    André, A. et al. A coherent all-electrical interface between polar molecules and mesoscopic superconducting resonators. Nat. Phys. 2, 636–642 (2006).

  29. 29

    Lim, J., Frye, M. D., Hutson, J. M. & Tarbutt, M. R. Modeling sympathetic cooling of molecules by ultracold atoms. Phys. Rev. A 92, 053419 (2015).

  30. 30

    Fitch, N. J. & Tarbutt, M. R. Principles and design of a Zeeman-Sisyphus decelerator for molecular beams. Chem. Phys. Chem. 17, 3609–3623 (2016).

  31. 31

    Wall, T. E. et al. Lifetime of the A(v′ = 0) state and Franck–Condon factor of the AX(0 − 0) transition of CaF measured by the saturation of laser-induced fluorescence. Phys. Rev. A 78, 062509 (2008).

  32. 32

    Dagdigian, P. J., Cruse, H. W. & Zare, R. N. Radiative lifetimes of the alkaline earth monohalides. J. Chem. Phys. 60, 2330–2339 (1974).

  33. 33

    Stuhl, B. K., Sawyer, B. C., Wang, D. & Ye, J. Magneto-optical trap for polar molecules. Phys. Rev. Lett. 101, 243002 (2008).

  34. 34

    Truppe, S. et al. An intense, cold, velocity-controlled molecular beam by frequency-chirped laser slowing. New J. Phys. 19, 022001 (2017).

  35. 35

    Williams, H. J. et al. Characteristics of a magneto-optical trap of molecules. Preprint at http://arxiv.org/abs/1706.07848 (2017).

  36. 36

    Weidemüller, M., Esslinger, T., Ol’shanii, M. A., Hemmerich, A. & Hänsch, T. W. A novel scheme for efficient cooling below the photon recoil limit. Europhys. Lett. 27, 109–114 (1994).

Download references

Acknowledgements

We thank J. Devlin for his assistance and insight. We are grateful to J. Dyne, G. Marinaro and V. Gerulis for technical assistance. The research has received funding from EPSRC under grants EP/I012044, EP/M027716, and EP/P01058X/1, and from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement 320789.

Author information

All authors contributed to all aspects of this work.

Correspondence to M. R. Tarbutt.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 341 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Truppe, S., Williams, H., Hambach, M. et al. Molecules cooled below the Doppler limit. Nature Phys 13, 1173–1176 (2017) doi:10.1038/nphys4241

Download citation

Further reading