Darmstadt 2008 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 27: Poster Quantengase

Q 27.2: Poster

Tuesday, March 11, 2008, 16:30–19:00, Poster C2

Bloch dynamics of a BEC: mean-field vs. microscopic descriptions — •Eva-Maria Graefe¹, Andrey R. Kolovsky², and Hans Jürgen Korsch¹ — ¹TU Kaiserslautern, Germany — ²Kirensky Institute of Physics, Krasnoyarsk, Russia

Recently much attention is paid to the Bloch dynamics of a BEC loaded into an optical lattice, subject to a static, for example, gravitational field. We compare two theoretical approaches to this problem, the mean-field description, based on the discrete nonlinear Schrödinger equation (DNLSE), and the microscopic description, based on the Bose-Hubbard model. Within the mean-field approach the main phenomena related to the Bloch dynamics are the dynamical instability (also known as modulation instability) and self-thermalization due to the onset of classical chaos in the DNLSE. We argue that the quantum manifestations of these phenomena are the depletion of the Floquet-Bogoliubov states, defined as the "low-energy" eigenstates of the evolution operator over one Bloch period, and the decoherence of the BEC. The correspondence between mean-field and microscopic description is analysed in dependence on the number of particles as well as on the magnitude and direction (for 2D or 3D lattices) of the static field.