title: Strongly interacting two-dimensional Bose gases.
abstract: We prepare and study strongly interacting two-dimensional Bose gases in the superfluid, the classical Berezinskii-Kosterlitz-Thouless (BKT) transition, and the vacuum-to-superfluid quantum critical regimes. A wide range of the two-body interaction strength 0.05 < g < 3 is covered by tuning the scattering length and by loading the sample into an optical lattice. Based on the equations of state measurements, we extract the coupling constants as well as critical thermodynamic quantities in different regimes. In the superfluid and the BKT transition regimes, the extracted coupling constants show significant down-shifts from the mean-field and perturbation calculations when g approaches or exceeds one. In the BKT and the quantum critical regimes, all measured thermodynamic quantities show logarithmic dependence on the interaction strength, a tendency confirmed by the extended classical-field and renormalization calculations.
authors.affiliation: The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Li-Chung
authors.initials: LC
authors.lastname: Ha
authors.affiliation: The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Chen-Lung
authors.initials: CL
authors.lastname: Hung
authors.affiliation: The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Xibo
authors.initials: X
authors.lastname: Zhang
authors.affiliation: The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA and Laboratoire Kastler Brossel, ENS, UPMC, CNRS UMR 8552, 24 rue Lhomond, 75231 Paris, France.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Eismann
authors.affiliation: The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Shih-Kuang
authors.initials: SK
authors.lastname: Tung
authors.affiliation: The James Franck Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA and The Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Cheng
authors.initials: C
authors.lastname: Chin