Quantum dynamics of atomic and molecular systems

Our group studies atomic and molecular quantum systems with respect to their interactions on different levels of complexity. Of special importance is the application and extension of modern methods for the manipulation and quantum control to many-body quantum systems, in particular using coherent light. The systems under investigation range from highly excited Rydberg atoms over atomic and molecular quantum gases to molecular aggregates. The group develops technologies for trapping and cooling of neutral atoms as well as quantum-state sensitive diagnostics.

Latest news from the lab

PhD-Meeting "FOR2247: From few to many body physics with dipolar quantum gases", 22-24.10 Heidelberg16.10.2018
Eleonora Lippi

From 22nd to 24th of October 2018 the PhD-Meeting of the Forschergruppe "FOR2247: From few to many-body physics with dipolar quantum gases" will take place at the Internationales Wissenschaftsforum Heidelberg (IWH) in Heidelberg. During the meeting, we are honoured to have lectures given by Prof. Dr. Tilman Esslinger and Prof. Dr. Olivier Dulieu concerning long-range interactions in systems of cavity-confined ultracold atoms and ultracold polar molecules.

For more information:
Website: FOR2247

A detailed analysis of the role of the intraspecies scattering length in the Efimov scenario has been published in Phys. Rev. A07.07.2017

In a joint experiment and theory work we study the effect of the intraspecies scattering length onto the heteronuclear Efimov scenario, following up on our earlier observation of Efimov resonances in an ultracold Cs-Li mixture for negative and positive Cs-Cs scattering length. Three theoretical models of increasing complexity are employed to quantify its influence on the scaling factor and the three-body parameter: a simple Born-Oppenheimer picture, a zero-range theory, and a spinless van der Waals model. These models are compared to Efimov resonances observed in an ultracold mixture of bosonic 133Cs and fermionic 6Li atoms close to two Cs-Li Feshbach resonances located at 843 G and 889 G, characterized by different sign and magnitude of the Cs-Cs interaction. By changing the sign and magnitude of the intraspecies scattering length different scaling behaviors of the three-body loss rate are identified, in qualitative agreement with theoretical predictions. The three-body loss rate is strongly influenced by the intraspecies scattering length.

S. Häfner et al., Role of the intraspecies scattering length in the Efimov scenario with large mass difference, Phys. Rev. A 95, 062708, or see our full list of publications
The PhD work of Juris Ulmanis published in the book series Springer Thesis 10.03.2017

Juris Ulmanis from the mixtures team receives the Springer thesis award for his PhD work. Congratulations!

His thesis explores the Efimov scenario, which is one of the prime examples of how fundamental quantum physics universally transpire across seemingly disparate fields of modern science. Initially speculated for nuclear physics more than 40 years ago, the Efimov effect has become a new research paradigm not only in ultracold atom physics but also in molecular, biological and condensed matter systems. In his work, Juris used a heteronuclear mixture of ultracold Li and Cs atoms to measure the scaling factor, which is a hallmark property and sometimes referred to as the “holy grail” of Efimov physics. These results allowed to pioneer experimental understanding of universal properties that unify the description of different three-body systems, as well as to discern microscopic, non-universal properties that sets different systems apart.

The book features a completely rewritten introduction that is aimed at young scientists just starting in the field of few-body physics. On top of a light primer on the Efimov effect, it highlights aspects of three-body physics in ultracold quantum gases and places these ideas in a wider context touching nuclear, atomic, and molecular physics. The rest of the work closely follows the original thesis.

For more information:
Read the book on Springer Theses

For more highlights see our news page

Research topics

Mixtures of ultracold atoms and molecules

In this experiment we use a mixture of two different alkali metals: cesium and lithium. This gives us the possbility to form ultracold LiCs dimers. These molecules have an extremely large electric dipole moment which promises many new experiments. For example, the molecules can be orientated in an external electric field.

Strongly-correlated Rydberg quantum gases

Rydberg atoms are atoms in highly excited electronic states. These atoms are very sensitive to external fields and experience extremely strong interactions with other Rydberg atoms. This gives us a model system for studying strongly-correlated quantum systems that is highly controllable and completely governed by interatomic interactions.

Collisions of highly charged ions and cold atoms

We are currently setting up this new experiment. Our goal is to investigate multiple electron capture using the combined techniques of magneto-optically cooling and trapping of the target atoms and using recoil ion momentum spectroscopy.

Hybrid ion atom trap for cold chemistry experiments

Interactions between ions and neutrals play an important role in all kind of chemical reactions. In order to gain a full understanding of these systems we are trying to observe reactions at ultra-low temperatures. In this regime the reaction dynamics are no longer concealed by the thermal movement of the particles.

Rydberg physics with ultracold two-electron systems

We are setting up an experiment to study the physics of two-electron Rydberg atoms using a quantum gas of ultracold strontium. The experiment is located at the University of Science and Technology of China (USTC Shanghai Institute for Advanced Studies). First studies will be aiming to explore many-body effects induced by the long-range interactions between highly excited strontium Rydberg atoms, using the inner electron to control the atom's motion and to detect single Rydberg atoms.