Résumé
Dipolar interactions are fundamentally different from the usual van der Waals forces in real gases. Besides the anisotropy, the dipolar interaction is nonlocal and as such allows for self-organized structure formation similar to the Rosensweig instability in classical magnetic ferrofluids. In the experiments with quantum gases of Dysprosium atoms performed in the team of the seminar speaker, the formation of a droplet crystal was observed. In contrast to theoretical mean field based predictions, the superfluid droplets did not collapse. It was confirmed experimentally that this unexpected stability is due to beyond-mean-field quantum corrections of the LeeHuang-Yang type. Self-bound droplets in three dimensions were also observed, which can interfere with each other. These droplets are 100 million times less dense than liquid helium droplets and they open new perspectives as a truly isolated quantum system. Under strong confinement in one dimension, the formation of a striped phase was also observed, with random mutual phases between the stripes.
