Final Report Summary - QUANTSTRO (Quantum-Degenerate Strontium:Mixtures, Molecules, and Many-Body Physics)
The ERC CoG project QuantStro explored ultracold Rb-Sr mixtures, leading to the discovery of new types of magnetic Feshbach resonances, built a Sr quantum gas machine with microscopy capability and was crucial to consolidate the research group of Florian Schreck. The overarching goal of QuantStro and the projects that continue its work is quantum simulation of many-body systems. This goal is pursued along two research lines: ultracold RbSr molecules and Sr quantum gas microscopy.
Heteronuclear ground-state molecules can have a large electric dipole moment, giving rise to strong, anisotropic long-range interactions. These interactions lead to highly interesting quantum many-body physics in gases of ultracold molecules. So far only alkali dimers were produced in the ultracold regime, which don’t have a magnetic dipole moment in their absolute ground state. By contrast, RbSr molecules have a magnetic dipole moment, which should enable more control over interactions between molecules. Creating an ultracold gas of molecules is usually done by cooling atomic gases to quantum degeneracy and then associating atom pairs into molecules. In QuantStro we explored mechanisms to associate Rb-Sr atom pairs into molecules. We spectroscopically investigated relevant optical molecular transitions and vastly increased the knowledge of the molecular ground-state potential. We improved STIRAP molecule association and increased Sr_2 molecule association efficiency from 30% to 80%, but also understood that this method is unsuitable for RbSr. We then searched for and discovered magnetic Feshbach resonances in Rb-Sr, which are originating from unusual mechanisms. We are currently upgrading the apparatus in order to exploit these resonances for magnetoassociation of Rb-Sr atom pairs into RbSr molecules.
We furthermore built a new Sr quantum gas apparatus, which is equipped with a high resolution microscope objective. We obtained quantum gases in this new apparatus and used it to determine the frequency of a mHz-linewidth optical transition to within 0.5MHz relative to an iodine transition, which is over 200x better than the previous determination. This transition can be used for nuclear spin state specific manipulation of Sr atoms. Using the microscope objective, we have implemented optical tweezers in which we can prepare individual Sr atoms.
Following its spirit as an ERC CoG, this grant has allowed me to consolidate my research group. I have obtained a full professorship position at the University of Amsterdam and was able to acquire substantial follow-up funding, guaranteeing the continuation of the projects described above and the further extension of my research into new areas, see http://www.strontiumbec.com/(opens in new window).
Heteronuclear ground-state molecules can have a large electric dipole moment, giving rise to strong, anisotropic long-range interactions. These interactions lead to highly interesting quantum many-body physics in gases of ultracold molecules. So far only alkali dimers were produced in the ultracold regime, which don’t have a magnetic dipole moment in their absolute ground state. By contrast, RbSr molecules have a magnetic dipole moment, which should enable more control over interactions between molecules. Creating an ultracold gas of molecules is usually done by cooling atomic gases to quantum degeneracy and then associating atom pairs into molecules. In QuantStro we explored mechanisms to associate Rb-Sr atom pairs into molecules. We spectroscopically investigated relevant optical molecular transitions and vastly increased the knowledge of the molecular ground-state potential. We improved STIRAP molecule association and increased Sr_2 molecule association efficiency from 30% to 80%, but also understood that this method is unsuitable for RbSr. We then searched for and discovered magnetic Feshbach resonances in Rb-Sr, which are originating from unusual mechanisms. We are currently upgrading the apparatus in order to exploit these resonances for magnetoassociation of Rb-Sr atom pairs into RbSr molecules.
We furthermore built a new Sr quantum gas apparatus, which is equipped with a high resolution microscope objective. We obtained quantum gases in this new apparatus and used it to determine the frequency of a mHz-linewidth optical transition to within 0.5MHz relative to an iodine transition, which is over 200x better than the previous determination. This transition can be used for nuclear spin state specific manipulation of Sr atoms. Using the microscope objective, we have implemented optical tweezers in which we can prepare individual Sr atoms.
Following its spirit as an ERC CoG, this grant has allowed me to consolidate my research group. I have obtained a full professorship position at the University of Amsterdam and was able to acquire substantial follow-up funding, guaranteeing the continuation of the projects described above and the further extension of my research into new areas, see http://www.strontiumbec.com/(opens in new window).