Dipolar Quantum Gas of NaK Molecules

Dipolar Quantum Gas of NaK Molecules

Strongly-interacting dipolar quantum gas of 23Na40K ground-state molecules

In our Lab, we are able to create dipolar quantum gases of NaK molecules by assembling ultracold mixture of sodium and potassium atoms. Their strong and anisotropic long-ranged intraction allows us to investigate the rich physics of dipolar many-body system in a strongly-interacting regime. We are particularly interested in the following three directions.


Understanding the many-body physics of a Bose-Fermi mixture is crucial to make quantum gas of 23Na40K polar molecules.  Such mixtures with different quantum statistics are fascinating in their own right because of its rich phase diagram with distinguishing features compared to pure fermionic or bosonic systems.  However, Bose-Fermi mixtures in the strongly-interacting regime remained largely unexpored in experiments due to severe collisional losses . Recently we have developed a species-dependent dipole trap technique which allows us to investigate the quantum phase transition of a density-matched Bose-Fermi mixture and produce a degenerate Fermi gas of NaK molecules.

We want to understand various collisional processes of molecules and atoms which are crucial to cool and stabilize molecules. We use external electric fields to tailor the long-range part of the molecules interaction in order to make strongly-interacting stable molecular quantum gas.  Recently we have loaded NaK molecules into a dark box trap in order to investigate the photon-induced loss of non-reactive bialkali molecules. Surprisingly we found a descrepancy at least two orders of magnitude with the latest collision model. more
We trap molecules in optical lattices to simulate novel spin models and extended Hubbard model beyond nearest-neighbor interactions. In our previous works, we have extended the rotational coherence time of polar molecules to 10 ms by using a spin-decoupled magic trap. Therefore we observe a density-dependent decoherence which is an evidence of dipolar interaction of molecules in a bulk gas. more


Starting from hot vapors of sodium and potassium at 330 and 50 degrees Celsius respectively in ultra-high vacuum chambers, we first produce a mixture of sodium and potassium atoms at about 100 μK in two-species magneto optical traps. To achieve quantum degeneracy, we perform evaporative cooling first in a pluged magnetic trap and then in an optical dipole trap. We can prepare a density-matched mixture of Bose-Einstein condensate of 0.8 × 105 sodium and deeply-degenerate Fermi gas of 2 × 105 potassium at about 100 nK in a species-dependent dipole trap. The Bose-Fermi mixture is then associated to 50000 long-lived weakly-bound Feshbach molecules at 0.3 Fermi temperature by ramping the magnetic field through a Feshbach resonance and transferred to the rovibronic ground state via stimulated Raman adiabatic passage (STIRAP). This gives us a good starting point for studying novel spin models with strong dipolar interactions in optcial lattices.

Our Sodium laser system

A picture of our yellow sodium MOT.

And a picture of our Potassium MOT.

Our vacuum system



January 2022  Our paper of  evaporative cooling of NaK molecules in 3D on arxiv!

November 2021 Our paper of degenerate NaK fermionic molecules on arxiv!

June 2021 Our paper of [new STIRAP technique] on arXiv. Here we show how filter cavities can improve the STIRAP efficiency! 

April 2021 Fermionic NaK polar molecules entered the quantum degenerate regime! Paper in preparation, stay tuned!

Transition from a mixutre of 23Na atoms (upper row) and 40K atoms to a degenerate Fermi gas of 23Na40K Feshbach molecules (lower row) .

September 2020 First ultracold polar molecules in a box trap! 

Na atoms (left) and NaK molecules (right) trapped by the 866-nm ring beam which forms the horizontal wall of the 3D box trap.

March 2020 Our new all-solid-state STIRAP laser system ready!  Well done Akira!

We are always looking for motivated undergraduate, Master and PhD students. If you are interested of  joining us, please contact Prof. Bloch (immanuel.bloch(at)mpq.mpg.de) 

Selected Recent Publications

Bause, R.; Kamijo, A.; Chen, X.; Duda, M.; Schindewolf, A.; Bloch, I.; Luo, X.: Efficient conversion of closed-channel-dominated Feshbach molecules of 23Na40K to their absolute ground state. Physical Review A 104 (4), 043321 (2021)
Bause, R.; Schindewolf, A.; Tao, R.; Duda, M.; Chen, X.; Quemener, G.; Karman, T.; Christianen, A.; Bloch, I.; Luo, X.: Collisions of ultracold molecules in bright and dark optical dipole traps. Physical Review Research 3 (3), 033013 (2021)
Bause, R.; Li, M.; Schindewolf, A.; Chen, X.-Y.; Duda, M.; Kotochigova, S.; Bloch, I.; Luo, X.: Tune-out and magic wavelengths for ground-state 23Na40K molecules. Physical Review Letters 125, 023201 (2020)
Seeßelberg, F.; Luo, X.; Li, M.; Bause, R.; Kotochigova, S.; Bloch, I.; Gohle, C.: Extending Rotational Coherence of Interacting Polar Molecules in a Spin-Decoupled Magic Trap. Physical Review Letters 121 (25), 253401 (2018)

Seeßelberg, F.; Buchheim, N.; Lu, Z.-K.; Schneider, T.; Luo, X.; Tiemann, E.; Bloch, I.; Gohle, C.: Modeling the adiabatic creation of ultracold polar 23Na40K molecules. Physical Review A 97 (1), 013405 (2018)

Research Group Members

Roman Bause
Doctoral candidate
  • +49 89 3 29 05 - 284 (Office) // -273 (Lab) //
  • -279 (Prep lab)
Xingyan Chen
Doctoral candidate
  • +49 89 32905 293 (Office) // -273 (Lab) //
  • -279 (Prep lab)
Marcel Duda
Doctoral candidate
  • +49 89 3 29 05 - 629 (Office) // -273 (Lab) //
  • -279 (Prep lab)
Benedikt Heizenreder
Master Student
  • +49 89 3 29 05 - 284 (Office)
Dr. Xinyu Luo
Group Leader
  • +49 89 3 29 05 - 283 (Office) // -273 (Lab) //
  • -279 (Prep lab)
Dr. Andreas Schindewolf
  • +49 89 3 29 05 - 293 (Office) // 273 (Lab) //
  • -279 (Prep lab)

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