Mainz 2026 – wissenschaftliches Programm

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A: Fachverband Atomphysik

A 27: Ultra-cold Atoms, Ions and BEC III (joint session A/Q)

A 27.2: Vortrag

Donnerstag, 5. März 2026, 11:30–11:45, N 1

In-situ observation of density-wave ordering in strongly interacting Fermi gases — •Zeyang Xue, Gaia S. Bolognini, Tabea Bühler, Aurélien Fabre, Kyuhwan Lee, Timo Zwettler, Giulia D. Pace, Victor Helson, and Jean-Philippe Brantut — Institute of Physics and Center for Quantum Science and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

We study quantum many-body phenomena of strongly correlated fermions. Our setup includes atoms cooled to the degenerate regime and a high-finesse optical cavity. The atoms inside the cavity combine the short-range contact interaction between atoms with the cavity-mediated long-range interaction induced by atoms exchanging photons of the cavity mode. When the strength of the long-range interaction exceeds a critical threshold, the system undergoes a phase transition into a density-wave ordered state. The talk focuses on the first in-situ observation of density-wave ordering. The local density-wave information is extracted by a high-resolution microscope with a numerical aperture of 0.39. We obtain direct information about the phase transition order parameter by quantifying the density-wave modulation contrast. We further investigate the correlation between atomic and photonic signatures of the density-wave ordering phase transition by recording the amplitude and phase of the photonic signal through heterodyne detection. We anticipate further experimental implementations enabled by the high-resolution microscope. For instance, a digital micromirror device (DMD) to apply arbitrary trapping potentials to atoms.

Keywords: Strongly correlated fermion; Cavity-mediated long-range interaction; Density-wave ordering; In-situ observation