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4. July 2018 15:45

Dynamical Equilibration Across a Quenched Phase Transition in a Trapped Quantum Gas

Dr. I-Kang (Gary) Liu
Newcastle University, UK

We investigate the dynamical equilibration of an uncorrelated thermal Bose gas passing through a Bose-Einstein condensate phase transition. During such crossing, the system breaks its symmetry resulting in numerous uncorrelated regions separated by the spontaneously generated defects. The emergence of spontaneous defects formation obeys a universal scaling law with quench duration, well known as Kibble-Zurek mechanism. The ensuing re-equilibration stage is govern by the evolution and interactions of such defects under system-specific and external constraints. We perform a detailed numerical characterization of the entire non-equilibrium process in an elongated ultra-cold Bose gas with fully three-dimensional classical-field simulations, addressing subtle issues and demonstrating the quenched-induced decoupling of condensate atom number and coherence growth during the re-equilibration process. Our findings agree with experimental observations made at the later stage of the quench, and provide the information via useful dynamical visualization in currently experimentally inaccessible regimes.