Dresden 2009 – wissenschaftliches Programm
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SYAL: Symposium Anderson Localization in Nonlinear and Many-Body Systems
SYAL 1: Anderson Localization in Nonlinear and Many-Body Systems
SYAL 1.5: Hauptvortrag
Montag, 23. März 2009, 16:00–16:30, BAR SCHÖ
Localized states and interaction induced delocalization in Bose gases with quenched disorder — •Thomas Nattermann — Institute for Theoretical Physics, Universität zu Köln,Zulpicher Str. 77, 50937 Köln, Germany
Zero temperature properties of a dilute weakly interacting d-dimensional Bose gas in a random potential are studied. We calculate geometrical and energetic characteristics of the localized state of a gas confined in a large box or in a harmonic trap. Different regimes of the localized state are found depending on the ratio of two characteristic length scales of the disorder, the Larkin length and the disorder correlation length. Repulsing bosons confined in a large box with average density n well below a critical value nc are trapped in deep potential wells of extension much smaller than distance between them. Tunneling between these wells is exponentially small. The ground state of such a gas is a random singlet with no long-range phase correlation For n>nc repulsion between particles overcomes the disorder and the gas transits from the localized to a coherent superfluid state. The critical density nc is calculated in terms of the disorder parameters and the interaction strength. For atoms in traps four different regimes are found, only one of it is superfluid. The theory is extended to lower (1 and 2) dimensions. Its quantitative predictions can be checked in experiments with ultracold atomic gases and other Bose-systems.