Hannover 2016 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 53: Quantum Gases: Fermions I
Q 53.9: Talk
Thursday, March 3, 2016, 16:30–16:45, e001
Observation of the Berezinskii-Kosterlitz-Thouless transition in an ultracold Fermi gas — •Puneet Murthy1, Igor Boettcher2, Luca Bayha1, Dhruv Kedar1, Mathias Neidig1, Martin Ries1, Andre Wenz1, Gerhard Zürn1, and Serlim Jochim1 — 1Physikalisches Institut, Ruprecht-Karls-Universität Heidelberg, 69120 Heidelberg — 2Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, 69120 Heidelberg
We report on the experimental investigation of the first-order correlation function of a trapped Fermi gas across the quasi-two-dimensional BEC-BCS crossover. We demonstrate that even in the inhomogeneous trapped system, the correlation function shows a qualitative change in behavior from an exponential to power law decay. The extracted scaling exponents show substantial deviations from BKT theory for homogeneous systems. Furthermore, we find the maximal scaling exponent at the transition to show no dependence on interaction strength, suggesting that the corresponding phase transitions lie in the same universality class. On the BEC side, our findings are validated by Quantum Monte Carlo computations for bosons. Near the resonance, the observed algebraic decay is not captured by the bosonic picture, indicating the crossover to a fermionic superfluid.