Hannover 2020 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 22: Posters: Quantum Optics and Photonics II
Q 22.54: Poster
Tuesday, March 10, 2020, 16:30–18:30, Empore Lichthof
Pairing on the BEC side of a fermionic system — •Manuel Jäger1, Thomas Paintner1, Daniel Hoffmann1, Wolfgang Limmer1, Michele Pini2, Pierbagio Pieri2, Giancarlo Strinati2, and Johannes Hecker Denschlag1 — 1Universität Ulm, Institut für Quantenmaterie, Deutschland — 2University of Camerino, School of Science and Technology, Physics Division, Italy
We investigate the pair formation in a two-component fermionic system on the BEC side of unitarity. In the limit of weak interaction and low density, those "preformed pairs" can be approximately described by a bound state of two fermions of opposite spin. In the vicinity of the Feshbach resonance, however, the many-body character of the pairs becomes important. This strongly interacting many-body regime is still not fully understood.
For investigating this system experimentally, we use a spin-balanced mixture of the two lowest 6Li Zeemann states and set their interaction strength by means of the Feshbach resonance at 832 G. We then measure the fraction of paired atoms at different temperatures and interaction strengths using optical spectroscopy. Our results are compared with an ab initio t-matrix calculation and a self-consistent thermal equilibrium model based on quantum statistics and effective mean field interaction. Our comparison reveals a separation between the molecular two-body and the many-body regime, although the measured pairing fraction is a thermodynamic quantity, rather than a dynamical one such as the pseudo-gap. In addition our results are used to further improve our statistical model.