Innovative method for stabilizing a gas of bosonic molecules

Ultracold dipolar molecules are a platform to fundamentally study quantum physics and realize new quantum technologies. Dealing with high inelastic loss rates is a challenge for realizing quantum gases of molecules. Recently, fermionic molecules in their ground state were successfully stabilized using external fields. Gases of bosonic molecules offer complimentary quantum applications, but they suffer from much faster inelastic loss. Researchers from the Institute for Molecules and Materials (IMM) of Radboud University, together with researchers from Columbia University (USA) managed to stabilize a bosonic gas with strong dipolar properties, greatly reducing losses and extending the lifetime. The results have recently been published in Nature Physics.

Evaporating molecules to a quantum gas requires reducing collisional loss rates. For fermionic molecules this has recently been achieved by “microwave shielding” which induces repulsive interactions between the molecules. Similarly reducing collisional loss for bosonic molecules is challenging because they can collide at ultracold temperatures without the centrifugal barrier that gives fermionic molecules additional protection. Therefore, orders of magnitude improvement in the protection of these molecules is required.

Bosonic gas

The research team demonstrated an order of magnitude improvement in ‘shielding’ in collisions, which should enable efficient evaporation. This greatly reduces losses and extends the lifetime to around 1 second. They also measured high scattering rates and their anisotropy due to dipolar interactions, which are central to the applications of ultracold molecules. The work has been performed in collaboration with the group of Professor Sebastian Will (Columbia University, USA).

Quantum phenomena

The findings represent an important step towards achieving a Bose-Einstein condensate of polar molecules into the lowest quantum energy state, paving the way for exploring highly correlated states of dipolar quantum materials. This can lead to the advancement of unique quantum phenomena and is a crucial in the study in physics, which have applications in areas such as the development of new materials and quantum technologies.

Figure: Illustration of the experiment on microwave shielded NaCs molecules and their interactions
Figure: Illustration of the experiment on microwave shielded NaCs molecules and their interactions.
Literature reference

Collisionally stable gas of bosonic dipolar ground-state molecules
Niccolò Bigagli, Claire Warner, Weijun Yuan, Siwei Zhang, Ian Stevenson, Tijs Karman & Sebastian Will
Nature Physics (2023)
Collisionally stable gas of bosonic dipolar ground-state molecules | Nature Physics

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Dr Karman, T. (Tijs)
Innovation, Molecules and materials, Science