Is there a physical difference between “left” and “right”? One might assume that the laws of nature do not care about spatial orientation. Yet since the 1950s, we have known that the weak interaction, which plays a role in various nuclear processes, does not behave perfectly symmetrically. This has profound implications for fundamental particle physics — and is connected to the question of why matter exists in the first place.

Prof. Tim Langen from the Institute of Atomic and Subatomic Physics at TU Wien has proposed a new experimental approach to address such fundamental questions: he uses special molecules that can be controlled with extraordinary precision. At temperatures near absolute zero, these molecules respond to extremely small effects of the weak interaction. For this research, Tim Langen has now been awarded a Consolidator Grant from the European Research Council (ERC).

Cold Molecules as a Tool for Particle Physics

Large particle accelerators such as CERN’s LHC have provided essential insights into the fundamental laws of particle physics. Tim Langen now investigates similar questions using compact precision experiments in the lab. “We use barium monofluoride. It is an ideal test molecule for us,” he explains. “It is heavy enough to make tiny effects measurable, yet it can still be cooled and trapped relatively easily.” In recent years, his research group has achieved key breakthroughs that now make such experiments possible.

Barium monofluoride molecules are confined in traps created with laser light, where they can remain in a stable quantum state for comparatively long periods. They can be driven into a rotational state that is extremely sensitive to the weak interaction. In this way, the team aims to measure how strongly the weak force differentiates between ‘left’ and ‘right’.

Although this difference has been known for decades, its exact magnitude remains uncertain: the few experiments performed so far have yielded inconsistent results.

This question is of great importance for modern particle physics — and ultimately for all of us. The symmetry breaking between left and right is indirectly linked to another symmetry breaking: the violation of matter–antimatter symmetry. If matter and antimatter had behaved in exactly the same way after the Big Bang, equal amounts of both would have been created and subsequently annihilated — leaving no matter in the universe today. Our very existence therefore depends on tiny asymmetries in the laws of nature, some of which can now be explored with unprecedented precision using Tim Langen’s cold molecules.

Tim Langen

Tim Langen leads the research division for Cold Molecules and Quantum Technologies at the Atominstitut at TU Wien. He studied physics in Mainz and Marseille and received his PhD from TU Wien in 2013, working on the dynamics of one-dimensional quantum gases. Research stays took him to the École Normale Supérieure in Paris, to JILA in Boulder (USA), and to the University of Stuttgart, where he established his own independent research group. His work has received numerous awards, including the Rudolf Kaiser Prize, an ERC Starting Grant, and an ERC Proof-of-Concept Grant. Since 2023, he has been a professor at TU Wien, where he is building a broad research program in the field of cold molecules.

Contact

Prof. Tim Langen
Institute for Atomic and Subatomic Physics
TU Wien
+43 1 58801 141750
tim.langen@tuwien.ac.at

Text: Florian Aigner