Regensburg 2004 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 10: Critical Phenomena

DY 10.3: Vortrag

Montag, 8. März 2004, 10:15–10:30, H2

Quantum Phase Diagram for Bose Gases — •Hagen Kleinert¹, Axel Pelster¹, and Sebastian Schmidt² — ¹Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany — ²Department of Physics, Yale University, P.O. Box 208120, New Haven, CT 06520-8120, USA

We locate the quantum phase transition for a dilute homogeneous Bose gas in the plane of s-wave scattering length a_s and temperature T. This is done by improving a lowest-order result for the thermodynamic potential with the help of recent high-order perturbative calculations on the leading shift of the critical temperature due to a weak atomic repulsion using variational perturbation theory. The quantum phase diagram shows a nose above the interaction-free critical temperature T_c⁽⁰⁾, so that we predict the existence of a reentrant transition above T_c⁽⁰⁾, where an increasing repulsion leads to the formation of a condensate. Furthermore, we obtain a similar quantum phase diagram for a bose gas trapped in an optical lattice as a function of effective scattering length a_eff and temperature T.

[1] H. Kleinert, S. Schmidt, and A. Pelster, cond-mat/0307412