Düsseldorf 2007 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 64: Poster Quantengase
Q 64.3: Poster
Donnerstag, 22. März 2007, 16:30–18:30, Poster C
Nonequilibrium dynamics of an ultracold lattice Bose gas — •Thomas Gasenzer1 and Kristan Temme1,2 — 1Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, 69120 Heidelberg — 2School of Physics & Astronomy, University of Leeds, Leeds LS2 9JT, United Kingdom
The dynamical evolution of a Bose-Einstein condensate trapped in a one-dimensional lattice potential is investigated theoretically in the framework of the Bose-Hubbard model. The emphasis is set on the far-from-equilibrium evolution in a case where the gas is strongly interacting. This is realized by an appropriate choice of the parameters in the Hamiltonian, and by starting with an initial state, where one lattice well contains a Bose-Einstein condensate while all other wells are empty. Oscillations of the condensate as well as non-condensate fractions of the gas between the different sites of the lattice are found to be damped as a consequence of the collisional interactions between the atoms. Functional integral techniques involving self-consistently determined mean fields as well as two-point correlation functions are used to derive the two-particle-irreducible (2PI) effective action. The action is expanded in inverse powers of the number of field components N, and the dynamic equations are derived from it to next-to-leading order in this expansion. This approach reaches considerably beyond the Hartree-Fock-Bogoliubov mean-field theory, and its results are compared to the exact quantum dynamics obtained from the solution of the Schrödinger equation for small atom numbers.