Cold Molecules

5th Institute of Physics

Research group led by Prof. Dr. Tim Langen. Laser cooling of atoms and molecules for applications in many-body physics, chemistry and tests of fundamental symmetries.

Welcome to the Langen Group

We are currenly in the process of moving to the Atominstitut at TU Wien and the Vienna Center for Quantum Science and Technology. This page will no longer be updated! For the latest news from our lab visit our new website at

We explore cold atoms and molecules for quantum science and technology. Our goals include the use of dipolar molecules, to realize new forms of quantum matter and gain insights into the foundations of molecular collisions and chemistry. Moreover, we study molecules that facilitate tabletop precision searches for new physics beyond the Standard Model of particle physics. Finally, we also develop compact experimental setups to manipulate single atoms and molecules for technological applications.


We use laser cooling to bring atoms and molecules to ultracold temperatures. Laser cooling is a very well established technique for atoms, which is used extensively in many 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 also 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 transitions laser cooling can still be realized for many molecular species. 

In addition to our work on cold molecules we also contribute to quantum simulations using 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. 2024

    1. K. L. Marroquín, R. Wang, A. Allahverdian, N. Durand-Brousseau, S. Colombini, F. Kogel, J. S. Keller, T. Langen, E. R. Grant, Self-organization in the avalanche, quench and dissipation of a molecular ultracold plasma, Journal of Plasma Physics 90, 935900101-- (2024).
  2. 2023

    1. T. Langen, G. Valtolina, D. Wang, J. Ye, Quantum state manipulation and science of ultracold molecules, arxiv (2023), doi:arxiv:2305.13445.
    2. E. Pultinevicius, M. Rockenhäuser, F. Kogel, P. Groß, T. Garg, O. E. Prochnow, T. Langen, A scalable scanning transfer cavity laser stabilization scheme based on the Red Pitaya STEMlab platform, Rev. Sci. Instrum. 94, 103004 (2023).
    3. M. Rockenhäuser, F. Kogel, E. Pultinevicius, T. Langen, Absorption spectroscopy for laser cooling and high-fidelity detection of barium monofluoride molecules, Phys. Rev. A 108, 062812 (2023).
  3. 2022

    1. J. Fraxanet, D. Gonzalez-Cuadra, T. Pfau, M. Lewenstein, T. Langen, L. Barbiero, Topological quantum critical points in the extended Bose-Hubbard model, Phys. Rev. Lett. 128, 043402 (2022).
    2. M. Schmidt, L. Lassablière, G. Quéméner, T. Langen, Self-bound dipolar droplets and supersolids in molecular Bose-Einstein  condensates. Physical Review Research. 4 (2022), p. 013235.
    3. P. Ruchka, S. Hammer, M. Rockenhäuser, R. Albrecht, J. Drozella, S. Thiele, H. Giessen, T. Langen, Microscopic 3D printed optical tweezers for atomic quantum technology, Quantum Science and Technology 7, 045011 (2022).
  4. 2021

    1. 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).
    2. 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).
    3. 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).
    4. 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).
    5. 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).
    6. 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).
  5. 2020

    1. 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).
    2. 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).
  6. 2019

    1. 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).
    2. 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).
    3. 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).
    4. 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).
  7. 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, T. Schweigler, E. Demler, J. Schmiedmayer, Double light-cone dynamics establish thermal states in integrable 1D Bose gases, New J. Phys. 20, 023034 (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, M. J. Mark, Ultrakalt magnetisiert, Physik Journal 17, 35 (2018).
  8. 2017

    1. D. Reens, H. Wu, T. Langen, J. Ye, Controlling spin flips of molecules in an electromagnetic trap, Phys. Rev. A 96, 063420 (2017).
    2. 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).


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

Prof. Dr.

Head of Research Group

To the top of the page