Does it describe a new discovery or a new methodology that’s useful to others?

Both. Over the past ten years, collective modes have been extensively studied in trapped atomic BECs and revealed a lot of interesting physics. Our experiments show that collective modes provide very important insight into the physical behavior of a degenerate Fermi gas in the BEC-BCS crossover. The observation of an abrupt transition when changing the interaction strength in the gas marked an important step in the discovery of fermionic superfluidity.

  Could you summarize the significance of your paper in layman’s terms?

Much of the great interest in the BEC-BCS crossover arises due to its close relation with several fields of physics like quantum fluids, neutron stars, and most prominently, high- temperature superconductors. Similar to the Cooper pairing of electrons in a superconductor the formation of pairs of fermionic atoms in a dilute gas can, at sufficiently low temperatures, lead to a superfluid phase. In contrast to a solid, however, these ultracold gases allow a precise control of the conditions and therefore serve as ideal model systems.

Our measurements are a first step to understanding the dynamics of the gas in the BEC-BCS crossover. A detailed understanding of the BEC-BCS crossover might in the future lead to the development of materials that are superconducting at temperatures as high as room temperature.

I joined the group of Professor Rudi Grimm in autumn 2001 as a Ph.D. student only months after he had moved to the University of Innsbruck. After setting up the apparatus, we started to investigate the interaction in ultracold Fermi gases and continuously developed the set-up. A major breakthrough of our experiment was the formation of a molecular Bose-Einstein condensate in November, 2003. This molecular BEC now serves as an ideal starting point to investigate the BEC-BCS crossover.