Hannover 2010 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 58: Quantum Gases: Lattices II

Q 58.6: Vortrag

Freitag, 12. März 2010, 11:45–12:00, E 001

Real-Time Ginzburg-Landau Theory for Ultracold Bosons in Optical Lattices — •Tobias Graß1, Francisco Ednilson Alves dos Santos1, and Axel Pelster2,31Institut für Theoretische Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Institut für Physik und Astronomie, Karl-Liebknecht-Str. 24 14476 Potsdam, Germany — 3Fachbereich Physik, Universität Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg, Germany

Applying the Schwinger-Keldysh formalism to the Bose-Hubbard Model we derive a real-time Ginzburg-Landau theory at zero temperature [1]. Surprisingly, it reduces to the seminal Gross-Pitaevskii theory deep in the superfluid phase although it has been originally determined within a hopping expansion and should, therefore, be only applicable in the immediate vicinity of the quantum phase boundary. Furthermore, in an equilibrium application, we show that the particle-hole excitation spectra in the Mott phase merge continuously into corresponding excitation spectra of the amplitude and the phase of the order parameter in the superfluid phase, once the quantum phase boundary is crossed. Finally, we discuss as a non-equilibrium application that the damping observed within the collapse and revival experiments of Ref. [2] turns out to be due to the overall harmonic potential which confines the atoms inside a finite volume.

[1] B. Bradlyn, F.E.A. dos Santos, and A. Pelster, Phys. Rev. A 79, 013615 (2009)

[2] M. Greiner, O. Mandel, T. W. Hänsch, and I. Bloch, Nature, 419, 51 (2002)

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