Freiburg 2024 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 27: Phase Transitions

Q 27.7: Vortrag

Mittwoch, 13. März 2024, 12:45–13:00, Aula

Observation of spatial first-order coherence in an optical quantum gas in a box — •Leon Espert Miranda, Andreas Redmann, Kirankumar Karkihalli Umesh, Frank Vewinger, Martin Weitz, and Julian Schmitt — Institut für Angewandte Physik, Universität Bonn, Wegelerstraße 8, 53115 Bonn, Germany

The emergence of long-range correlations that span the entire system is a manifestation of phase transitions between different states of matter. Experimentally, such field correlations in quantum gases can be obtained by investigating the degree of first-order spatial coherence, for example, in interference experiments. Here we report a measurement of the build-up of quasi long-range correlations in a two-dimensional optical quantum gas trapped inside a box potential as the total number of particles in the gas is increased. The correlation information is obtained by measurements of the photon gas distribution in momentum space as well as interferometry of the dye-filled optical microcavity emission. We observe different scalings of the coherence length for the normal and quantum degenerate gas. Moreover, by studying different sizes of the box trap, we demonstrate that Bose-Einstein condensation sets in as soon as the coherence length exceeds the system size.