ERIK MCLEAN / UNSPLASH

Physikalisches Kolloquium

Freitag, 30. Mai 2025 17:00 Uhr  Mixed Quantum Gases: From Cold Collisions to Many-Body Physics in the Ultracold

Prof. Dr. Rudi Grimm, Center for Ultracold Atoms and Quantum Gases, Innsbruck, Austria

Ultracold mixtures combine atomic species with fundamentally different properties. Bosons can meet fermions, heavy particles can meet light ones, interparticle interactions can be controlled precisely by external fields, and novel quantum systems emerge with intriguing properties. Over the past 25 years, great progress to prepare various types of mixtures in the laboratory has opened up numerous excited research avenues, related to the few- and many-body physics of atomic and molecular quantum systems.

I will start with a brief review of early experiments carried out in the late 1990’s at the MPI for Nuclear Physics in Heidelberg on mixtures of lithium and cesium. These activities triggered many exciting further developments, including experiments in Heidelberg and Innsbruck on cooling and trapping techniques, thermodynamics, heteronuclear molecules, Efimov quantum states, and on the physics of quasi-particles.

In the main part of my talk, I will focus on the specific topic of quasi-particles called “Fermi polarons”, which we have extensively studied in Innsbruck with potassium atoms (bosonic or fermionic) immersed as impurities in a Fermi sea of lithium atoms. In a series of experiments over the past decade, we have explored the energy spectrum, the formation dynamics, decay and coherence properties, and mediated interactions between polarons. Ongoing experiments are dedicated to the motion of impurities after controlled kicks by photon momentum transfer. Most strikingly, we observe a motion-induced breakdown of the polaron above a critical momentum, where the particle gets “undressed” and becomes a bare particle.

Teilchenkolloquium

D** at Belle II

Dr. Markus Prim, Physikalisches Institut, Universität Bonn

Astronomisches Kolloquium

Dienstag, 3. Juni 2025 16:30 Uhr  The atmospheres of discs and planets

Barbara Ercolano , Ludwig-Maximilians-Universität, University Observatory Munich (USM) The gaseous atmospheres of extrasolar planets and those of their birth environments, the protoplanetary discs, may hold the key to understanding the observed diversity of these distant worlds and might provide important insights on fundamental questions, including habitability. In this talk I will review the results of recent efforts to connect the protoplanetary disc evolution, driven by their central star, to the formation of planets. Special attention will be given to outflows and what can be/ has been learnt from them. Some of the unanswered questions, rely on the understanding of the chemical composition of atmospheric gas, particularly with regards to important species like (polycyclic aromatic) hydrocarbons, that control the thermodynamics in the far ultra-violet regime and play an important role in the coupling of the atmospheric gas to magnetic fields. The same molecules may play a very important role in the evolution of planetary atmospheres. Current and future efforts to constrain their abundances in discs and planets will also be reviewed. To arrange a visit with the speaker during the visit, please contact their host: Kees Dullemond (ITA)

Zentrum für Quantendynamik Kolloquium

Mittwoch, 11. Juni 2025 16:30 Uhr  tba

Dr. Sylvain Ravets , Department of Photonics, Université Paris-Saclay