University of Amsterdam

ERC funded


Towards a quantum gas of RbSr ground-state molecules


RbSr illustration


Molecules have a richer internal structure than atoms and exhibit more intricate interactions. Both properties are highly valuable to create and study few- and many-body quantum systems beyond the reach of atoms. So far ultracold gases of alkali dimer molecules have been created. Our goal is to create a quantum gas of RbSr ground-state molecules. In contrast to alkali dimers, RbSr has three valence electrons, one of which is unpaired in the molecular groundstate. This endows RbSr with a magnetic dipole moment in addition to the electronic dipole moment also available in alkali dimers. These magnetic and electric dipole momenta are two handles with which we can control the molecules and create interesting few- and many-body systems.

To reach a quantum gas of ground-state molecules it will be necessary to cool an ultracold gas of molecules. We intend to cool by evaporation, which requires a large ratio of elastic to inelastic collisions. With RbSr it should be possible to create repulsive van der Waals interactions between the molecules in a relatively simple manner, making us hopeful that a quantum gas of molecules is within our reach. Such a quantum gas would be the perfect starting point to design many-body systems.

So far we have created lattice gases of Rb and Sr with many sites occupied by one atom of each species. To associate atom pairs to molecules we will use a stimulated Raman adiabatic passage, which we showed to work for this purpose by creating Sr2 molecules. We are currently performing photoassociation spectroscopy to find a viable molecule association path.


The Team

Premjith Thekkeppat, Mateusz Borkowski, Klaasjan van Druten and Florian Schreck

Former team member in Amsterdam: Alex Bayerle, Vincent Barbé, Alessio Ciamei, Lukas Reichs llner


More information

Powerpoint presention: RbSr.pptx (59MB).

PDF: RbSr.pdf (7MB).

Vincent Barbé introduced the RbSr project to his friends and relatives in a short lab tour video before his PhD defence (French with English subtitles):



Internship reports


Lab pictures


The vacuum chamber in which the experiments take place, surrounded by magnetic field coils and optics.



The heart of the apparatus, a glass cell vacuum chamber, surrounded by magnetic field coils and optics. The blue fluorescence of a 88Sr magneto-optical trap is visible as reflection in the glass cell.


last change: 29.08.2023 by FS