SAMOP 2023 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 50: Quantum Gases: Fermions I
Q 50.3: Talk
Thursday, March 9, 2023, 11:30–11:45, F342
Observation of Cooper pairs in a mesoscopic 2D Fermi gas — •Marvin Holten1,2, Luca Bayha1, Keerthan Subramanian1, Sandra Brandstetter1, Carl Heintze1, Philipp Lunt1, Philipp Preiss1,3, and Selim Jochim1 — 1Physikalisches Institut, Heidelberg University, Germany — 2Atominstiut, TU Wien, Austria — 3Max Planck Institute of Quantum Optics, Garching, Germany
The formation of strongly correlated pairs is fundamental for the emergence of fermionic superfluidity and superconductivity. To understand the pairing mechanism is an ongoing challenge in the study of many strongly correlated fermionic systems. In this talk, I present the direct observation of Cooper pairs in our experiment. We have implemented a fluorescence imaging technique that allows us to extract the full in-situ momentum distribution with single particle and spin resolution. We apply it to a mesoscopic Fermi gas, prepared deterministically in the ground state of a two-dimensional harmonic oscillator. Our ultracold gas allows us to tune freely between a completely non-interacting unpaired system and weak attractions where we find Cooper pair correlations at the Fermi surface. When increasing the interactions even further, the pair character is modified and the pairs gradually turn into tightly bound dimers. The collective behaviour that we discover in our mesoscopic system is closely related to observations in nuclear physics or metallic grains. Our method provides a new pathway to study many of the outstanding questions concerning fermionic pairing, for example in imbalanced systems or the normal phase.