title: Emergence of coherence via transverse condensation in a uniform quasi-two-dimensional Bose gas.
abstract: Phase transitions are ubiquitous in our three-dimensional world. By contrast, most conventional transitions do not occur in infinite uniform low-dimensional systems because of the increased role of thermal fluctuations. The crossover between these situations constitutes an important issue, dramatically illustrated by Bose-Einstein condensation: a gas strongly confined along one direction of space may condense along this direction without exhibiting true long-range order in the perpendicular plane. Here we explore transverse condensation for an atomic gas confined in a novel trapping geometry, with a flat in-plane bottom, and we relate it to the onset of an extended (yet of finite-range) in-plane coherence. By quench crossing the transition, we observe topological defects with a mean number satisfying the universal scaling law predicted by Kibble-Zurek mechanism. The approach described can be extended to investigate the topological phase transitions that take place in planar quantum fluids.
authors: Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 Place Marcelin Berthelot, 75005 Paris, France.
authors: Lauriane
authors: L
authors: Chomaz
authors: Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 Place Marcelin Berthelot, 75005 Paris, France.
authors: Laura
authors: L
authors: Corman
authors: Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 Place Marcelin Berthelot, 75005 Paris, France.
authors: Tom
authors: T
authors: Bienaimé
authors: Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland.
authors: Rémi
authors: R
authors: Desbuquois
authors: Institut für Laserphysik, Universität Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany.
authors: Christof
authors: C
authors: Weitenberg
authors: Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 Place Marcelin Berthelot, 75005 Paris, France.
authors: Sylvain
authors: S
authors: Nascimbène
authors: Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 Place Marcelin Berthelot, 75005 Paris, France.
authors: Jérôme
authors: J
authors: Beugnon
authors: Laboratoire Kastler Brossel, Collège de France, CNRS, ENS-PSL Research University, UPMC-Sorbonne Universités, 11 Place Marcelin Berthelot, 75005 Paris, France.
authors: Jean
authors: J
authors: Dalibard