Darmstadt 2008 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 15: Quantengase (Gitter I)

Q 15.1: Vortrag

Dienstag, 11. März 2008, 14:00–14:15, 1C

Bogoliubov vs. chaotic energy spectrum for Bose atoms in optical lattices — •Andrey Kolovsky — Kirensky Institute of Physics, 660036 Krasnoyarsk, Russia

Recent experiments with cold bosonic atoms in optical lattices has renewed the theoretical studies of the Bose-Hubbard model, which constitutes one of the fundamental Hamiltonians in the condensed matter theory. The number of phenomena, discussed in the frame of this model, is so diverse that sometimes it is difficult to see any link between them. In particular, this concerns the phenomena of superfluidity and Quantum Chaos. Indeed, the former phenomenon assumes the regular phononlike excitation spectrum, described by the Bogoliubov theory, while the latter phenomenon implies a highly irregular excitation spectrum, described by the random matrix theory. This seeming contradiction is resolved by noting that these two spectra refer to different characteristic energies of the system. In the talk I shall explain of how the regular Bogoliubov spectrum of the Bose-Hubbard system evolves into an irregular one as the system energy is increased. A manifestation of this transition for the excitation dynamics of the superfluid state of cold atoms in optical lattices is discussed as well [1].

[1] A. R. Kolovsky, Phys. Rev. Lett. 99, 020401 (2007); Phys. Rev. E 76, 026207 (2007).