5th Institute of Physics

Cold Molecules

Independent junior research group led by Dr. Tim Langen. Laser cooling of molecules for applications in many-body physics, cold chemistry and tests of fundamental symmetries.

Welcome to the Langen Group

Our goal is to exploit the strong and tunable dipole moments of diatomic molecules, to realize new forms of quantum matter and gain new insights into the foundations of molecular collisions and chemistry. Moreover, we study molecular species that facilitate precision searches for new physics beyond the Standard Model of particle physics, using only a small tabletop experiment instead of full-scale particle accelerators. 

For the latest news from our lab please click here!


We use laser cooling to bring molecules to ultracold temperatures. Laser cooling is a very well established technique for atoms, which is used extensively at our Institute and other labs around the world. It relies on the fact that atoms can repeatedly absorb and emit a large number of photons with the same wavelength. Intuitively, it seems very challenging to apply this technique to molecules because of their complex level structure, which e.g. includes many rotational and vibrational levels. However, by carefully chosing suitable molecular transitions laser cooling can still be realized for many species. 

In addition to our work on cold molecules we also contribute to the work on ultracold magnetic atoms at the institute, and collaborate with the 4th Physics Institute on trapping of single atoms in 3D-printed optical tweezers.


Project Publications

  1. 2021

    1. M. Schmidt, L. Lassablière, G. Quéméner, T. Langen, Self-bound dipolar droplets and supersolids in molecular Bose-Einstein  condensates (2021), (available at http://arxiv.org/abs/2111.06187).
    2. J. Fraxanet, D. Gonzalez-Cuadra, T. Pfau, M. Lewenstein, T. Langen, L. Barbiero, Topological quantum critical points in the extended Bose-Hubbard model (2021), doi:arxiv:2106.15457.
    3. F. Kogel, M. Rockenhäuser, R. Albrecht, T. Langen, A laser cooling scheme for precision measurements using fermionic barium monofluoride (137Ba19F) molecules, New Journal of Physics 23, 095003 (2021).
    4. J. Hertkorn, J.-N. Schmidt, M. Guo, F. Böttcher, K. S. H. Ng, S. D. Graham, P. Uerlings, T. Langen, M. Zwierlein, T. Pfau, Pattern Formation in Quantum Ferrofluids: from Supersolids to Superglasses, Physical Review Research 3, 033125 (2021).
    5. J. Hertkorn, J.-N. Schmidt, M. Guo, F. Böttcher, K. S. H. Ng, S. D. Graham, P. Uerlings, H. P. Büchler, T. Langen, M. Zwierlein, T. Pfau, Supersolidity in Two-Dimensional Trapped Dipolar Droplet Arrays, Physical Review Letters 127, 155301 (2021).
    6. J.-N. Schmidt, J. Hertkorn, M. Guo, F. Böttcher, M. Schmidt, K. S. H. Ng, S. D. Graham, T. Langen, M. Zwierlein, T. Pfau, Roton Excitations in an Oblate Dipolar Quantum Gas, Phys. Rev. Lett. 126, 193002 (2021).
    7. J. Hertkorn, J.-N. Schmidt, F. Böttcher, M. Guo, M. Schmidt, K. Ng, S. Graham, H. P. Büchler, T. Langen, M. Zwierlein, T. Pfau, Density Fluctuations across the Superfluid-Supersolid Phase Transition in a Dipolar Quantum Gas, Phys. Rev. X 11, 011037 (2021).
    8. F. Böttcher, J.-N. Schmidt, J. Hertkorn, K. S. H. Ng, S. D. Graham, M. Guo, T. Langen, T. Pfau, New states of matter with fine-tuned interactions: quantum droplets and dipolar supersolids, Reports on Progress in Physics 84, 012403 (2021).
  2. 2020

    1. D. Reens, H. Wu, A. Aeppli, A. McAuliffe, P. Wcisło, T. Langen, J. Ye, Beyond the limits of conventional Stark deceleration, Phys. Rev. Research 2, 033095 (2020).
    2. R. Albrecht, M. Scharwaechter, T. Sixt, L. Hofer, T. Langen, Buffer-gas cooling, high-resolution spectroscopy, and optical cycling of barium monofluoride molecules, Phys. Rev. A 101, 013413 (2020).
  3. 2019

    1. J.-F. Mennemann, T. Langen, L. Exl, N. J. Mauser, Optimal control of the self-bound dipolar droplet formation process, Computer Physics Communications 244, 205--216 (2019).
    2. M. Guo, F. Böttcher, J. Hertkorn, J.-N. Schmidt, M. Wenzel, H. P. Büchler, T. Langen, T. Pfau, The low-energy Goldstone mode in a trapped dipolar supersolid, Nature 574, 386--389 (2019).
    3. F. Böttcher, M. Wenzel, J.-N. Schmidt, M. Guo, T. Langen, I. Ferrier-Barbut, T. Pfau, R. Bomb\’ın, J. Sánchez-Baena, J. Boronat, F. Mazzanti, Dilute dipolar quantum droplets beyond the extended Gross-Pitaevskii equation, Phys. Rev. Research 1, 033088 (2019).
    4. F. Böttcher, J.-N. Schmidt, M. Wenzel, J. Hertkorn, M. Guo, T. Langen, T. Pfau, Transient Supersolid Properties in an Array of Dipolar Quantum Droplets, Phys. Rev. X 9, 011051 (2019).
  4. 2018

    1. I. Ferrier-Barbut, M. Wenzel, F. Böttcher, T. Langen, M. Isoard, S. Stringari, T. Pfau, Scissors Mode of Dipolar Quantum Droplets of Dysprosium Atoms, Phys. Rev. Lett. 120, 160402 (2018).
    2. T. Langen, M. J. Mark, Ultrakalt magnetisiert, Physik Journal 17, 35 (2018).
    3. H. Wu, D. Reens, T. Langen, Y. Shagam, D. Fontecha, J. Ye, Enhancing radical molecular beams by skimmer cooling, Phys. Chem. Chem. Phys. 20, 11615–11621 (2018).
    4. T. Langen, T. Schweigler, E. Demler, J. Schmiedmayer, Double light-cone dynamics establish thermal states in integrable 1D Bose gases, New J. Phys. 20, 023034 (2018).
  5. 2017

    1. T. Schweigler, V. Kasper, S. Erne, I. Mazets, B. Rauer, F. Cataldini, T. Gasenzer, T. Langen, J. Schmiedmayer, J. Berges, Experimental characterization of a quantum many-body system via higher-order correlations, Nature 545, 323–326 (2017).
    2. D. Reens, H. Wu, T. Langen, J. Ye, Controlling spin flips of molecules in an electromagnetic trap, Phys. Rev. A 96, 063420 (2017).


We are currently funded by an ERC Starting Grant, the Baden-Württemberg Stiftung, the Vector Stiftung, the Center for Integrated Quantum Science and Technology (IQST), the MWK Baden-Württemberg, and the University of Stuttgart.


Please see the teaching page of the institute.

We are always looking for new team members!

Student assistant (Hiwi) position during semester break:

The 5th institute of Physics is looking for students who would like to experience everyday work in a modern quantum optics laboratory.

A variety of techniques and skills will be used:

  • CAD Modelling / 3D printing
  • electronics
  • usage of optic devices/laser
  • measuring techniques

Previous experience with these techniques is an advantage but not a requirement.

Salary: normal Hiwi salary per hour, hours per week and schedule upon individual arrangement.

Interested candidates should contact Tim Langen.
Are you interested in realizing a new cutting-edge experiment at the forefront of quantum physics?
PhD position in
Laser Cooling of Dipolar Molecules
at the 5th Institute of Physics, University of Stuttgart

The goal of this thesis will be the construction of an experiment to directly laser cool and study diatomic molecules. The student will push state-of-the-art techniques to new limits in order to realize molecular gases in the quantum regime.

With applications ranging from quantum many-body physics to cold collisions and precision measurements, the creation of such gases will enable many fascinating insights at the interplay of physics and chemistry.

We are looking for candidates with a background in experimental techniques ranging from quantum optics and laser cooling to electronics and programming. The position is part of a collaborative environment in an international team, and fully funded by the ERC Starting Grant project NEWMAT.

If you are interested in learning more, please contact Dr. Tim Langen.

Please contact Tim Langen for further details.



This image shows Tim Langen

Tim Langen

Head of Research Group / Deputy Professor

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