Emergence of coherence via transverse condensation in a uniform quasi-two-dimensional Bose gas

• DOI: 10.1038/ncomms7162
• Publication Date: 2015-01-30T13:55:40Z
• Authors: Lauriane Chomaz; Laura Corman; Tom Bienaimé; Rémi Desbuquois; Christof Weitenberg; Sylvain Nascimbène; Jérôme Beugnon; Jean Dalibard
• Keywords: 13. Climate action; 0103 physical sciences; 01 natural sciences; 3. Good health

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.