Mainz 2017 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 21: Ultracold atoms and BEC - IV (with Q)
A 21.5: Vortrag
Mittwoch, 8. März 2017, 15:30–15:45, N 1
Quantum and thermal phase transitions in a bosonic atom-molecule mixture in a two-dimensional optical lattice — •laurent de Forges de Parny1,4, valy rousseau2, and tommaso roscilde3,4 — 1Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder Straße 3, D-79104, Freiburg, Germany — 2Physics Department, Loyola University New Orleans, 6363 Saint Charles Ave., LA 70118, USA — 3Institut Universitaire de France, 103 bd Saint-Michel, 75005 Paris, France — 4Laboratoire de Physique, CNRS UMR 5672, École Normale Supérieure de Lyon, Université de Lyon, 46 Allée d’Italie, Lyon, F-69364, France
Recent progress in ultracold gases have allowed the study of multiple component bosonic systems, such as atomic and molecular mixtures. We will show that the coherent coupling of the atomic and molecular state, can lead to a novel insulating phase - the Feshbach insulator - for bosons in an optical lattice close to a narrow Feshbach resonance. This new phase appears around the resonance, preventing the system from collapsing when the effective atomic scattering length becomes negative. Surprisingly enough, the transition from condensate to Feshbach insulator has a characteristic first-order nature, due to the simultaneous loss of coherence in the atomic and molecular components. Our realistic numerical study shows that these features appear clearly in the ground-state phase diagram of e.g. rubidium 87 around the 414 G resonance, and they are therefore directly amenable to experimental observation. We also observe unconventional Berezinskii-Kosterlitz-Thouless transition when heating the superfluids.