Hannover 2016 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 22: Quantum Gases: Bosons II

Q 22.6: Vortrag

Dienstag, 1. März 2016, 15:45–16:00, e001

Long-range correlations and superfluidity of the one-dimensional quasi-condensate — •Hansjörg Polster and Carsten Henkel — Institute of Physics and Astronomy, University of Potsdam, Germany

A Bose gas confined to two or one dimensions does not show any phase transition. Still, due to interactions, a smooth cross over is found when the density increases, signalled by a reduction of density fluctuations and an increase in the phase correlation length. We discuss exact results for correlation functions of the Bose field, obtained with the help of a mapping to a random walk in the complex plane [1,2].

When the Bose gas is rotated in a closed ring, discrete peaks emerge in the momentum distribution, defined by the winding numbers of the complex field. We discuss the disappearance of these peaks when the rotation velocity is increased and compare to Landau’s scenario of the breakdown of superfluidity. Full distribution functions are obtained for both local and global quantities like current density and total momentum.

[1] L. W. Gruenberg and L. Gunther, Phys. Lett. A 38 (1972) 463; D. J. Scalapino, M. Sears, and R. A. Ferrell, Phys. Rev. B 6 (1972) 3409

[2] I. Carusotto and Y. Castin, C. R. Physique 5 (2004) 107