Mainz 2017 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 15: Ultracold atoms and BEC - II (with A)

Q 15.7: Talk

Monday, March 6, 2017, 18:30–18:45, N 1

Pairing in the normal phase of a 2D Fermi gas — •Puneet Anantha Murthy, Mathias Neidig, Ralf Klemt, Marvin Holten, Luca Bayha, Philipp Preiss, Gerhard Zürn, and Selim Jochim — Physikalisches Institut, Universitaet Heidelberg

Paring of fermions is central to our understanding of superfluidity and superconductivity. In their celebrated work, Bardeen, Cooper and Schrieffer (BCS) describe how a pairing instability at sufficiently low temperatures at the Fermi surface leads to a transition from the normal phase to a superfluid for a weakly attractive Fermi gas. The formation of these Cooper pairs is a true many-body effect as it requires the presence of a Fermi sea and according to the BCS theory the pairing starts at the transition temperature. On this poster, we present evidence for pairing also in the normal phase of a two component 2D Fermi gas. We use spatially resolved radio-frequency (RF) spectroscopy to measure the onset of pairing at different interaction strengths across the 2D BEC-BCS crossover. We show that pairing occurs at temperatures significantly higher than the critical temperature for superfluidity. The spatially resolved RF spectroscopy allows us to separate the low- from the high-density regions of our inhomogeneous trap. As a result, we can identify regions where two-body physics is applicable and regions where many body effects take over. We map out a region in the strongly interacting regime, where paring is significantly influenced by the many-body nature of the system and cannot be explained purely by two-body physics.